Guitar-Pro is one of the better ones but it not a very general program: it is a little too focused around guitar tabs!

I use a combination of Guitar-Pro, ABCMUS and Harmony Assistant which together cover just about the whole range I am interested in. ABCMUS is good from reading SongWrite and converting them to ABC, which I can then read and manipulate with Harmony Assistant to finally export a MIDI file which can by imported to Guitar-Pro for polishing if I want. Equally, I can start in Guitar-Pro, export as MIDI and then use Harmony to get to ABC.

All of these three programs are pretty cheap and are available, I think, as shareware for evaluation.