Well, I use my computer for lots of stuff.
Games, Photos, Movies, Music, Docs, Spreadsheets, Internet...
But, I keep most of my media on external drives.
I plan to use the Mac for photo stuff initially, since I bought a Nikon D90 back in August, and then the Windows 7 partition for work and other non-Mac software I already have.
Then again, I can run that using Parallels...
I guess since this is my first Mac, I put that question back to the public... What am I going to use my Mac for?