I got it today and it's really awesome. I haven't tried the online yet, but I did play plenty of Split-Screen and a few levels of single player, and I have to say it's one of, if not the best FPS on the Wii. The Split-Screen reminds me so much of playing the original Goldeneye and Perfect Dark on my N64. It's really good. I love the classic controller controls, and my friend loves the GameCube controls so all is good. I really want to try the online, because if it's as good as Modern Warfare Reflex then it will be great. I would highly suggest the game.
I don't know about you, but I have the Homebrew Channel and I'm still on 4.2, and I have been playing games online for quite a while without any trouble. Maybe I'm just lucky though. I've heard that Nintendo can't do anything about it, and that they will only ban you if you cheat online, which I don't. Even then it's possible to change your information and unban yourself with a fair amount of ease...