SL brings a significant amount of content to the table. The level cap is increased by ten. Each "calling" receives a new soul which in many cases brings a totally new playstyle to that calling. For example, the mage now has access to the Harbinger soul which turns the mage into a melee based class (and is a ton of fun.) I found the cleric's Defiler soul a bit underwhelming, and the warrior's Tempest didn't really appeal to me because I've played so many ranged classes in the past, but overall each new soul brings something worthwhile to the table. There are a handful of new dungeons with respective expert (heroic) modes, and of course new raid content as well. SL also adds two new continents to Telara. Taken together, these two are roughly equal to the "old" content of Mathosia and the Ember Isle, so SL essentially doubles the size of the game world. Overall you are getting a considerable amount of content.
Which brings us to another "good." You can basically get this for free. Yes, I know RIFT itself will be free-to-play in a couple weeks, but if you want to get in "early," the aforementioned Raptr promotion is still running. So if you are willing to put up with their
Overall you really can't beat the "value" that SL offers. It gives you a lot of things to do. Trion has done a lot of things over the past year or so to try and improve things like PvP (Conquest mode) and group PvE (Instant Adventures) and while these are not features of SL specifically, they are all things that benefit from what this expansion brings to the table. And in the end, isn't that what an expansion is really all about? It's about making the core game itself better and more enjoyable. Yes there needs to be content, but underneath it all there needs to be a game worth playing and SL does a good job of "complimenting" the experience that is RIFT. Unlike some other recent expansions that basically made me give up a five year investment in the game and want to gouge out my eyeballs (I'm looking at you Cataclysm.)
One last thing I'll begrudgingly include as a good aspect of SL is its questing model. I know it has been much maligned (especially for the reliance on the new Carnage quests) and there are some issues that I have with it as well and I will talk about those in a minute. But the overall model itself is perfectly serviceable, and in my opinion still an improvement over the model used in the core RIFT game. Old RIFT was much like any other themepark MMO in terms of questing. You ride into a town, you see a bunch of people with "!" over their heads, you go do a bunch of random tasks, and you collect loot and XP. Standard stuff. SL changes this model in that the number of quests is significantly reduced. The typical pattern in SL is you obtain a central story quest at the quest hub, then when you get to the quest area you will find quest items lying around and an associated quest to collect them, and then one or more Carnage quests that involve killing the mobs that inhabit that area. So rather than a quest hub being a "forest of '!'" there is usually one central quest and the associated quests are handled differently. Now I do have issues with Carnage, but as I said, overall I enjoy this presentation more. It allows you to focus a bit more on the story being told and not on all the "fetch and gather" kinds of side quests.
Nothing is perfect, and SL is no exception. There are some major issues with this expansion. Now just as a disclaimer, I have not "completed" everything in SL yet. So if some of my complaints are addressed later, please feel free to let me know, but this is how I see things right now. One of the biggest problems in SL for me is scaling. This is a problem for any expansion as you have to adjust the new content for a variety of players... those who spent a lot of time at the old level cap, those who did not, those who obtained a lot of high level gear, and those who did not. That said, SL's scaling feels like a brick wall at times. My warrior was fairly well geared at level 50. I was not a raider, but I had a good amount of high level crafted gear and items from expert dungeons and the associated currency. I was not walking around in "quest greens" when I hit the SL content. I had a good solo spec (copied from a forum guide, I will admit) and good gear... but SL still hit me like a ton of bricks. I died a few times within the first few quests in the SL starting zone. I can't imagine how difficult it might be for someone who is in "quest greens" and not spec'd properly.
Now at first you might attribute this to perhaps a failing of skill, or unfamiliarity with the game after coming back, or various other issues. And you might be right... except that it happened again as soon as I hit the next "tier" of zones. I finished both SL intro areas (something I would recommend everyone should do) but as soon as I moved to the next zone, I ran into the same issue I had at the beginning. I got massacred several times within the first group of quests in each zone. Ok, so fool me once... shame on me. I'll chalk up the first time to my failings. But for the same thing to repeat itself a few levels down the road? Nope, shame on you this time, Trion. The scaling of the content is just not good. The mobs have tons of HP and hit like trucks... and I was running a very survivable build. I'm all for my MMO's being "dangerous." I don't want to faceroll all the content in it. But to be greeted by significantly tougher mobs that essentially slam a door in your face every time you enter a new zone is not the way to encourage people to play your game. It can be very offputting.
Which brings us to my biggest problem with SL as a whole. I had heard about and read about how much of a "grind" the leveling in SL was and I had hoped it was an overstatement. I had hoped it was just the "sour grapes" of people spoiled by games like WoW which basically do everything in their power to get you to max level quickly. I had hoped that things in SL worked at a reasonable pace. I was wrong. SL is a horrific grind. Now granted Trion does give you a fair amount of selection in terms of what you will grind. You can do every single Carnage quest you come across. You can babysit outposts and do Onslaughts. You can chain queue PvP Warfronts. You can run IA's all day. But regardless of what you choose, you will grind... and grind... and grind. Focusing solely on the story based quests and even the associated side quests will not allow you to progress sufficiently to move from hub to hub and zone to zone. You will need to do more.
Like the scaling issue above, SL's pacing is horrendous. After finishing both of the introductory zones (and doing all Carnages and a few Onslaughts) I was level 52. After completing one of the next tier of zones, I was halfway to level 53. The amount of XP needed per level is just obscene, and it becomes more so with each step towards level 60. The Planar Attunement (alternate advancement) system does give you the feeling that you are still advancing your character, albeit slowly, but the levels themselves absolutely crawl by. The end result is that the content feels tedious. You feel forced to do things that you might otherwise enjoy. This is really my problem with the concept of Carnage quests. It is one thing if I choose to do them because I'm a "completionist," or I want the associated achievement, or some other kind of reward. But they don't feel like a choice. They feel like something I have to do simply to play the game. I was working on some quests last night and when I got my third different Carnage in a particular area... I just sighed and logged off in the middle of no where. It was pretty disheartening.
Despite its shortcomings, I do think SL is a good expansion to a good game. I'm not in a hurry to get to the new cap. I'm not a raider anymore. I can't sit around and farm dungeons all day. So for me the grinding aspects are more of an annoyance than a true impediment to enjoying the game. Sure I'd like it if the content were tuned a bit better, but it isn't a deal breaker. And when taken in comparison to what Bioware/EA foisted on us with Hutt Cartel, at least Trion gives you a lot more bang for your buck, and you sure as heck can't beat "free" which is what SL essentially is now.