The vast majority of guitarists still use those ASCII tabs, not Guitar Pro -- but, fair point!
The biggest problem with Guitar Pro is that the playback is synthetic/MIDI. Our philosophy is that learning from a real recording is the best (only?) way to catch subtleties of music like phrasing, timing and feel.
I've been using Guitar Pro for most the time that I've been playing guitar and bass, and the fact that the playback is Midi has not been much of an issue (and I wasn't sold on Guitar Pro 5 "real sound engine" or whatever it was called). Though I've been playing bass which has less subtleties in my main genre (rock/metal). Even with guitar the heavy lifting for me is to learn what fingers goes where on the fretboard. After that, I can listen to the actual song and polish whatever nuances I feel that I need, without referring to the tab (since I know where the fingers goes on the fretboard at this point).
Oh come on - you guys even mention Guitar Pro on the About page. This is like building a word processor and then comparing it to Notepad.