My macbook has been running great. Although every now and then it seems to get pretty hot. I check activity monitor to find that both of the cores are running at about 50% load each. Yet no process seems to be taking up anywhere near that much (even combined). I've tracked it down to "Windows Sharing". For some reason, maybe samba has gone crazy or something, but switching off Windows Sharing seems to bring it right back down to a normal temperature. Once you've turned off Windows Sharing you can turn it back on and have no issues. It mainly seems to happen after coming out of sleep. I'll have to try and track down the main reason to the problem. Some software bug somewhere (this is on 10.4.6). I didn't have this problem on my g4 ibook. Although this is really the only problem with my macbook, and it is very minor.