One very small annoyance that we were hitting regularly in TFS 2008 was trying to diff file which didn't have pending change. Assuming that we want to see changes checked in on a server, we would need to specify some less than trivial parameter:

"tf diff foo.txt;W~T"

If there was a pending rename involved, it would fail and we will need to specify both paths separately:

tf diff foo.txt;W~T