I used Xandros for a while, and it was godly awful. Like a slug, Xandros Desktop takes a whole 3-5 minutes to boot fully, then a further 60 seconds to log in. Only thing that ran fast on it was Mozilla Firefox and some form of an Office suite. I’m more of a Windows person ;)
However, I have not seen other forms of Linux as yet, so I can’t really pass comment on the main bulk of Linux OS’s; Xandros is just one of many!