I use Roll20 exclusively for my GURPS games. I tried Fantasy Grounds and Battle Grounds but the user community at Roll20 is far superior and it is free to all players plus it works on any OS since it is web interface..
I only wish that SJGames would support and endorse Roll20. I have started a thread on it asking for them to at least make an official presence by developing a GURPS character sheet for Roll20.
http://forums.sjgames.com/showthread.php?t=153115
t least I wish they would comment on VTTs and if that is somethign they are looking into.