Right now I'm using Finale 2008. I like experimenting with different instruments, though at the moment guitar and piano are my favorite combination. I just need to remember to turn down the volume bar on the staff a bit so the guitar isn't so fucking loud. Speaking of guitars, I have a TAB for Radical Dreamers, so I might do that later.
I once also took a pure piano part for READY, STEADY, GO! from Fullmetal Alchemist and turned it into a mostly brass piece. Of course, that was back in the olden days when I was still using Microsoft MIDI Synthesizer, so it came out like shit. I should redo that...