I use this set-up for WoW.
Logitech G15 Keyboard (the old one with 18 G keys)
This keyboard has worked flawlessly for me so far (4 years I think). Literally the only problem I've had is the paint is wearing off my ASDW keys. It's doesn't affect anything though. As far as I know the Space bar is reinforced for extreme mashing. Mine is still working like it was on day 1.
Logitech MX Revolution Wireless
This mouse has worked really well for me. It has the two scroll wheels. The top scroll wheel has a fast scroll option where if you click it down and then flick it, it spins super fast. I have abilities hot-keyed to the two side buttons and the top button. It's very comfortable for long gaming sessions (ICC Heroic raids). I also hotkeyed abilities to the scroll wheel (Healthstone for scroll up and Barkskin for scroll down).
The only issue with this mouse, and it's very minor, is if I have my TV remote in between the mouse and the receiver it can lag the mouse movements. It's very easy to fix this issue.
Overall I've always been happy with Logitech products for gaming.
Edit: The mouse has a Li-ion battery instead of AA. Even after a day of heavy use it still has 2/3 bars left. I just throw it on the charger every night when I shut my computer down.