Mostly a "deep in the guts" kind of guy rather than UI type stuff. Most of my time has been spent on C/C++ and networking, though I was an early adopter of NeXTStep/ObjC/Appkit back in the day, and am finding my way back with the iPhone. I've spent a lot of time doing distributed systems using various technologies, including working with a team on an open-source CORBA ORB.
I don't do Windows. I've tried. Several times. We've just agreed to disagree, and the first thing I install is Cygwin.
I use a Mac as my primary machine, though most of my time currently is spent working on vxworks and linux.