As far as a major contender distribution that I use on a regular basis, I would say it would definatly have to be Simply Mepis 7.0. Mepis is a rock solid distribution created by Warren Woodford, and the Mepis Team.
Read it here
The only issues that I have ever ran across with Simply Mepis is the wireless driver for my Linksys USB Wireless G Adapter not being included. However this was simply fixed by using ndiswrapper to install the rt73 windows driver.