I've been using Finale for several years, but after a friend demo'd the new Sibelius 6 to me, I immediately ordered it! (As a teacher I got it from Academic Software for $159 as a "competitive crossgrade.") It may take a while to learn all the keyboard shortcuts, but it overall seems superior to Finale. One element of Finale that bugs me is sometimes when I insert measures, various expression marks don't shift, so they are now not aligned with the intended passages! And worse, sometimes the voices no longer line up!

Which notation software do most major publishers use? (Schirmer, Boosey & Hawkes, etc.)

Outside of notating the score, I've used Cubase and messed around with Garage Band to record actual audio tracks.