I've got the Microsoft Wireless Laser 7000 desktop set. Love the keyboard, hate the mouse.
Some genius @ Microsoft decided to put a AAA size battery in the mouse. Idiotic thing to do apparently - the mouse is all the time having lag issues, swapping battery sometimes fixes it.
Finally gave up and went with the Logitech G9 Lasermouse
and LOVE it. Yes, it's wired but when you move the mouse, the pointer moves - precisely. Best mouse I've ever had by a long shot, the weights and changable cover are great. The G9 has lots of good reviews - that's how I decided to try it.
I now use the MS wireless keyboard and the Logitech wired mouse. Very happy with this combo.