I received an invitation to the third Rift beta event, currently running, and I like the game. And instead of compiling a list like everybody else what Rift copied from what other game (UI from WoW, public quests from WAR, etc.), I'd like to say that it seems that Trion copied the secret sauce recipe from Blizzard: Don't worry too much about originality and features, but rather spend your time making sure that everything that is in the game works perfectly. Rift in beta is more polished than most MMORPGs that came out in the last 3 years on release.
And I do believe that this is the way to go for a MMORPG to have any kind of success in today's market. The buggy crap people put up with a decade ago simply doesn't cut it any more. A new game easily survives snide remarks in reviews that its user interface looks exactly like WoW's, but it doesn't survive its user interface being cumbersome, laggy, and non-intuitive, however innovative and original it might be. Just look what happened to Final Fantasy XIV!
Being polished these days is a necessary (but not sufficient) condition for any MMORPG wanting to enter the market. Trion's Rift fulfills that condition, and thus I do think the game will do just fine. Not a "WoW Killer", but a game that will sell well and keep up a good number of subscribers.