I have a Genius Wireless optical mouse with 5 buttons (3 of which I don't use) a scroll wheel (best thing since sliced bread) and a battery charger built in to the receiver. If it didn't have a battery charger it would eat a set of batteries a week. Works great, but!
It was a combo with a wireless keyboard which has just gone crazy and had to be shot.

There were issues with it which I'm wondering if they are common to all wireless keyboards -
1. There was a really annoying delay between pressing shift and getting capitals to type.
2. At random times it would repeat the last key over and over and over and ... you get the idea.
Soltek QBIC, Pentium 4 3.0GHz, 512MB RAM, 200GB SATA HDD, ATI Radeon 9600XT 256MB, Netgear 54Mb/s WAP, ridiculously expensive Satellite Broadband
Windows XP Home SP2, Trend Micro Internet Security, Firefox, Thunderbird, AdAwareSE, Spybot S&D, SpywareBlaster, A-squared Free, Ewido Security Suite.