XFS is fast, but I wouldn't use it as the OS's filesystem as it has a lot of cache issues making it far less reliable during a crash. I have used XFS for my storage drives as it is very fast at deleting large files, which is very important for Myth and the like. However, I won't do it again. I have lost a lot of files because of XFS and it doesn't have the ability to resize well, so if you use RAID (like lvm2) then it's definitely not the right choice! I think ext3 is a sane choice.