I am developing an online strategy game using .Net v2. Although the game is primarily strategic, it does have some tactical elements that require reasonable network performa
I'd also like to note that "Games for Windows", which XNA uses on windows with its Live! networking APIs is now free ... which means that if you write an XNA game that uses the networking features, your users do not have to have a gold membership :-)
http://www.engadget.com/2008/07/22/games-for-windows-live-now-free/
If you're new to game development, I'd recommend XNA- it's easy to program with. The advantage of Torque, however, is it has asset creation tools, which can also be invaluable. For a higher end game or FPS, the Source engine is great.