SD appears to freeze when copying very large files (e.g. my 14 gig Parallels drive image). I finally figured out it was not in fact frozen by using the 'sudo lsof | grep SDCopy' terminal trick.
The reasons I believed that SD was frozen were that the data in the "copy files" section was stuck, and checking out SDCopy in Activity Monitor gave a "not responding" feedback.
It would be very helpful to have some sort of progress updater showing that SD is in fact just in the middle of copying a giant file, and not to worry.
I know, i should just walk away from the computer and stop watching it, but hey, that's just not me