Personally, I think the 2A03 is a bit overdone, and moreover Famitracker does a very good job with emulating many of its nuances. Still sounds good though.
Try making raw 1-bit music with the ZX Spectrum beeper next, given that Follin started with that. :V
I can just whip out my gameboy and play stuff on the go and the sound is much more authentic than using vst's and such. I'm using a game for the gameboy that is uniquely designed to produce music and push it to its limits.
Ah, so I guess purity of sound is one of the factors in your work, then?
This makes other chips difficult, though a few have hardware implementations outside original hardware (notably the SIDStation and the Yamaha DX200, latter being a portable DX-7 + drum machine for live gigs).