I purchased an MS LASER 6000 a couple of days ago and installed the Intellimouse 5.4 drivers. It was a total fiasco. The drivers never would allow me to switch to a left handed use pattern but stuck both primary buttons with right clicking. (Yes I'd assigned click to the right hand button before changing the left button settings.)

I had done an uninstall of USB Overdrive prior to my MS install so that conflict wasn't an issue. Attempting to eliminate the MS drivers was worse. After a thorough scouring of my boot system for any related files I never was able to reinstall USB Overdrive and have it functional. In fact the Apple mouse drivers were messed up!

MS seems to have an awful tendency to write software which completely dominates any computer in which its installed. After a couple of hours messing around, I finally gave up and just eliminated the system and copied over my back-up clone which was only a day old. Moving a few e-mails and a couple of new image files and I was back to 'normal' having never been able to assess the mouse or drivers. (They work great on my PC.)

Although I have to believe my experience couldn't possibly be universal and the drivers must have been tested on Macs before release, I strongly suggest that if one uses a Mac don't use these drivers! Get USB Overdrive.