I haven't had much networking issues between OSX and Win XP. In fact, file transfer rate is so much faster but that is very much 'hardware-capable'

You won't find any issues with your Graphic (Adobe) softwares as there's a version for Mac and they're pretty 'solid' but for your 3D stuffs, well, I guess xandman's given you a little insight.

I wouldn't recommend a Mac to a gamer though