Well having put some considerable amount of time into this last night, I'll post my impressions for those on the fence etc.
The Good
The class system is amazing, really well thought out and implemented, the diversity you can achieve in what you wanna play and roles you can fulfill is great, naturally there are more efficient combos for doing a single role then others but unless your looking into min maxing this isn't a problem.
The Rift mechanic is cool, I wasn't expecting it to take off the way it did because of player apathy, but I logged into people calling out rift positions on maps for high level rifts that they needed assistance in closing. Also they happen frequently enough that you don't have to go looking for them if you don't want to, and the big invasion style rifts, are an excellent touch. Here's an example of my map during on of these invasions, took about an hour and 20 minutes to get everything cleared up, was insanely fun.
Invasion Map
I haven't had the chance to venture into the dungeons and such yet, so I can't comment on that but judging from what people have been talking about in general chat it seems like the standard fare.
The Bad
I'm not sure what it is about the character models, but they just don't look good, I can't really put my finger on it but something about them just seems very unpolished, and it applies to the general graphical quality in the game as well. It isn't really a horrible thing but, it just comes off to me as not being very fluid, in movements to the clay like environments. I'm playing with everything on ultra and maintaining around 60fps but again just comes off to me as not right, however I do enjoy the art style of WoW quite a bit which may be it.
In any case the game is fun, despite being very similar to a certain other MMO it has a unique enough spin to differentiate itself, would definitely recommend trying it out if your least bit interested in MMOs