Personally, I'm just looking for a new world to explore. The end game is probably the thing I want to see the most. I'm also intrigued by the Rift tradeskill system and am looking forward to exploring what it has to offer. During the first 2 Betas I haven't wanted to spend any time with crafting as my main goal was just to level to 20 and play with the rifts, etc. However, from what I've seen in small glimpses, it looks like there will be quite the intricate crafting system in Rift.
Aside from these items, I'm looking forward to the game in general. I know a few people on other threads have complained or more or less said they weren't impressed with the graphics but aside from a short list of bugs I think the game looks pretty amazing.
As for unique game play, MMO, etc., I don't know that I would say RIFT is doing anything extraordinary or revolutionary. I don't mean that in a bad way at all. Honestly, aside from the day when we can all strap on a pair of virtual glasses and it look as though we are truly in the game, I don't see how any MMO can really be that much different by way of groundbreaking newness. I mean traditionally they're all going to have quests, they're all going to be aimed at some sort of levelling or evolution style platform to ultimately reach an ambiguous end game playing field.
Personally, I'm 100% ok with that. I think what it comes down to is finding the game that is right for you. Ultimately you should be happy with enough aspects of the game to want to play it. For me, RIFT meets that criteria and I'm looking forward to it's release. I think Trion has taken a lot of what is out there and have done a great job of improving on many of these areas.