avi seems to be the preferred format, but any video file can be checked using bitzi look up. Right click on the file in the search window and select.. (I think) more options..> check with bitzi look up. This will take you to a web site which will rate the file according to others who have sent in reports.
See this link
http://www.gnutellaforums.com/showthread.php?t=37676
A film is usually over 700MB and if this gets to you in three hours that sounds pretty good to me