There are a few features Gom has that are missing in VLC, the first major one is the ability to play playlists. You can queue up files to be played which saves you having to get up every time a short video ends. The other main distinguishing feature is its ability to play broken or incomplete files.
If you are half way through downloading a file and wanted to check its quality, or just have a damaged video file Gom's patented technology will quite happily play back any information it can find when other players will grumble and not even attempt to open the file.
Gom is definitely worth checking out and could well be a big competitor to VLC very soon, bring on a Mac version!
Gom Player
NB. upon writing this I have just noticed that Gom have released a free video encoder capable of many different formats. Although I havent tested this myself, if this is anywhere near as good as Gom Player it should be pretty special.