It's only a gimmick if it's not used properly. What I'm worried about is if the transition from a dual-analog stick controller the Wii remote doesn't work out as well as everyone hopes. I'd have to see which one worked better, since I have both systems.
Also, to prevent double posting, I'll edit this in: the first day is finally over, and what really surprised me is just how many really great-looking games are coming out this holiday season. So far the games that have excited me most so far have been Assassin's Creed and Mass Effect, but I have not yet seen Super Mario Galaxy, Bioshock, or Fallout 3 in action. Other games I saw that looked cool: Mercenaries 2 (so very many explosions), Fracture, Burnout Paradise, and (somewhat surprisingly) the Simpsons.
Call of Duty 4 looked absolutely amazing graphically, but I don't know if there's anything particularly unusual about the gameplay, but if you like shooters that's probably one you'll want. Me, I want my shooters to be a little more off-the-wall.
Tomorrow's Sony's day to shine: Gamespot's got live demos of just about all of their first party stuff. This may make or break my decision on the PS3 for this holiday.