People often are interested in the development platform being used. Here is my current setup:
Debian GNU/Linux : Squeeze (Testing)
iBook G4 (14")
--1.33 MHz CPU
I am a novice programmer, and my roots in programming are in my C and C++ classes in college, where we were instructed using a text editor like vi or nano and constructed our own make files, and compiling from the command line. My development tool has progressed from nano to Gedit. It has color mapping and brace/bracket/parentheses matching for most programming languages, which is all I need. I haven't yet attempted an SDK of any sort since my current commandline based environment has become comfortable.
Software most used (in no particular order):
qjackctl for control of jackd
Hydrogen Drum Kit
...and of course
Some people are afraid of switching to Linux because they have to sacrifice many familiar Windows applications. In my experience, I sacrificed little and gained much by switching to Linux.