Most online games are free to play once you buy the game, like Call of Duty (WW2 FirstPersonShooter) and Battlefield (WW2 shooter, the same system as StarWarsBattlefront)... Unfortunately games like Galaxies require a periodic subsription or something... Let's hope you don't have to pay Lucas on a monthly basis - because in that case I may not re-subsribe legally.
And Yes, definately get it on PC. In my experience, ported games (on PS2, XBox) end up sucking majorly compared to the PC versions.
One really good aspect about online play is that there is a possibility that you can make custom models/skins and custom maps/planets/vehicles. Who knows! I'm excited.