The controls take some getting used to. I played through the GC version quite a bit, so I may be holding the Wii controls to an unfair standard--that is, the level of comfort I had with the GC controls. I'm going to give it another week.
It does seem to take an extra round or two if all you're doing is pumping bullets into people. In addition, it seems to me that they've made kneecapping a little harder in that when you cap now, goons have a tendency to just fall flat on the ground instead of kneeling before the Almighty Leon, Dealer of Death. Or maybe I'm just rusty.
Overall, though, I don't feel like zombie killin' for the Wii has been more or less difficult than on the GC: it's been cap, kick, knife-knife-knife up until I quit after Del Lago. The Del Lago fight went damn quick thanks to the ease of Wiimote aiming.
The only thing that may be more than my imagination is that I felt like I got a lot of (2) drops for shotgun and rifle ammo instead of (5) drops. Ah well. And the screen is definitely cut off in 16:9. I'm no A/V whiz, but I can see it on the screen. In spite of that, I think the graphics still hold up well for being 3 years old. I know I'm alone in that, but hey.
I'm looking forward to playing my way through that extra PS2 content. Mercenaries, however, can kiss my ass.