I took a look at the Rift Open Beta yesterday. Here are my impressions. I didn't get very far, only to about level 7 or so.
Rift is very similar to World of Warcraft and similar quest-driven fantasy MMOs. Trion has deliberately made the interface very familar to WoW players, using much the same hotkeys and layout. This is a positive, in my view.
Rift's major innovation is its class system. You start by picking a fundamental archetype: Warrior, Cleric, Mage, or Rogue. Then you pick up to three sub-classes, called souls, which focus on different aspects of the base archetype.
It's an interesting system, and in a lot of ways is opposite to the direction that WoW has taken. WoW characters focus on a specific specialization: Holy Paladin versus Retribution Paladin. In contrast, Rift is aiming at the combination of souls taken.
We will see how successful they are. WoW's drive for specialization was driven by the playerbase, because it produced optimal results.
I created a Malthusian (human) Warrior. I choose the Paladin/Warlord/Void Knight souls, pretty much creating a sword-and-shield tank.
Gaining abilities in Rift depends on your souls. Each soul is like a talent tree you can invest talent points in. But each talent tree also has a "root" line of abilities. As you invest points in the talent tree, new abilities are unlocked along the root line. So if you put more points in the Paladin tree than the Warlord tree, you unlock more Paladin abilities than Warlord abilities.
Abilities themselves are pretty standard MMO fare so far. Some have cooldowns, debuffs, buffs, reactive abilities etc. Warrior use a combo-point system with generators and finishers.
All in all, it's a very clean system. However, there are a few issues. First, you still have to buy ranks in each ability, so you have to go to a trainer every so often. It seems like this is just extra complexity. Unlocking abilities through talent points was enough, and I think it would work better if your abilities just automatically scaled with your level.
Second, there's a lot of front-loaded complexity. Each soul comes with starter abilities. For example, I have 3 different basic combo-point generator at level 7, and about 5 different buffs. I'm using the Warlord generator and a paladin finisher, and just dropped the other two off my bars. But the sheer number of buttons available at level 7 is a bit overwhelming.
Finally, warriors theoretically have a resource bar, called Power. But so far, Power seems to regenerate faster than I can spend it, so you're really limited by the global cooldown and ability cooldowns. The resource doesn't seem to matter.
First, the game is very responsive. No input lag or discontinuity between pressing buttons and results. Animations are solid and fun to watch.
The graphics are pretty decent, but they draw from the green/brown/gray "realistic" palette and thus are not very vibrant or crisp.
As well, apparently Trion belongs to the camp that believes that female plate armor does not need to cover vital areas like the chest or stomach. At least they aren't in high heels, though.
In-game, the performance is very good. I'm not 100% certain that I have the graphics set right, but I set them to Good and everything plays well with a decent framerate.
Oddly though, my system can't seem to handle the cutscenes. I get massive framerate stutters during cutscenes. It's really weird considering that in-game performance is excellent.
Rift seems like a pretty decent game. It's pretty polished and plays well so far. I haven't really gotten into the Rifts part, which seem to be like Warhammer's public quests, or instancing or anything really advanced.
If you're looking for something majorly different than WoW, than Rift is probably not for you. But personally, I'm a fan of choosing one thing to change and then doing a great job with that single change, and that is what Trion is aiming for with their class system.