The gun attachments are awkward and they limit the buttons that are accessible.
I have the Wii Zapper and it's bleh.
How's your cursor tracking? If it's shaky or it jumps when rotating, you're either too far from the sensor bar, or background lights are causing interference. If you go into the Wii tracking settings and see more than 2 white dots, you'll need to turn off background lights.
If the above isn't an issues and the cursor just feels like it's off from your hand's movement, then moving the sensor bar about half way between you and the TV will help. it also can take a bit to get used to.
If you can get your sensor bar's placement good for your TV, you'll find that it's pretty good for shooters. But I need to note that the smaller the screen, the better, it brings the tracking closer to 1:1.
I really like the Wii for FPS, it adds a level of fun. I've been using mice way longer though.
Is this the new COD:WoW? I've been interested in getting this game, but I can't justify the Wii's price tag, when I can get it on my PC and I know that none of my other friends will buy it for the Wii. I also read that its cursor tracking isn't as good as Medal of Honor 2 or Metroid Prime 3, both of which I have and both are great.