Ive been gaming on a wireless mouse since about 2003 when any lag problems went away.
The main benefit of course is no lead to worry about, I guess no one else is bothered but it often knocked my aim off.
The worry about batteries is minor in comparison, even more so now as a modern mouse will run off one battery if needed and do so for a fortnight or more
Plus you can have multiple mice on modern windows anyway afaik, keep an old one connected as backup if needed
My original Logitech is still working, wasnt cheap but over that time it can hardly be called bad value.
So I recommend you look into just Logitech mice, even if not specifically called a gaming mouse I think they all likely good. I also have a Mx600 and it works fine too. Maybe you can find a cheap bundle
You need a good gaming mat for the mouse to glide
http://www.overclockers.co.uk/produ...&catid=23&sortby=priceAsc&subid=1276&mfrid=60
Best keyboard for gaming is a small one. You will be using one hand and in Arma2 I use every key on the board. So smallest is best. The one I use is very cheap, designed for carrying with a laptop.
I can span all keys with one hand, caps lock to enter at the same time. Ergonomically most people will be most settled with hands 1 foot apart not 2 as a large gaming board with numpad would force them to sit (if right handed)