I'm using the latest Kubuntu edgy beta. My MSI S260 laptop was running on battery and the fan would turn on for a second, then off again, then on for a couple of seconds, then off again, etc. It didn't seem normal at all, so I rebooted to Windows, where the problem didn't occur, then rebooted to Kubuntu again and the fan went crazy again. I ran |watch -n 1 'acpi -t'|, which showed me the fan turned on whenever the CPU temperature went above 60°C, and as soon as it dropped below that, it turned off again. Unfortunately, one second of cooling seemed to be enough to make it drop, after which it would almost immediately go above 60 again, creating an infinite loop. There should be some sort of grace/threshold. I thought the BIOS controlled this sort of thing, but, like I said, I'm not experiencing this issue on Windows.
Just to clarify, I'm not sure if this happens with the adapter plugged in, and if charging/using the battery has anything to do with it. The fan is pretty quiet, and there's enough ambient noise not to notice. Still, this sort of thing can probably break a fan, so I think it should be fixed before the Edgy release.