I use a cheapie - an A4tech cordless optical mouse which came as part of an inexpensive cordless mouse/keyboard set.
Works a treat, no delay and if you reduce the speed of the cursor you can get one pixel accuracy if you need it.
The keyboard's ok too - multimedia and all that.
You can spend a lot, but in my experience there's no need to spend heaps of your hard-earned.
Cheers
AA