Welcome Ilvarin, and I fully support you move to GIMP. I am still quite a noob with the software but man I'll tell you, there is allot you can do with this powerful bit of software. And the fact that it's open source makes it that much more cool. Well, there are some great GIMP mapping walk-through's in the tutorials section, and RobA has come up with a number of really helpful GIMP scripts and plug-ins, so be sure to check those out as well. Well, looking forward to seeing your first WIP.

Cheers,
-Arsheesh