What are some alternatives?
When comparing GetHarmony.net and GUITAA, you can also consider the following products
yalp.io - Automatic chords extraction from mp3 and YouTube
Chordify - Chordify turns any music or song (YouTube, Deezer, SoundCloud, MP3) into chords.
ChordU - Extracts chords from any song, integrated YouTube.
Amazing Slow Downer - !A slow down music software for Mac and Windows computers - Amazing Slow Downer
Guitar Dashboard - Open-source interactive music theory for guitarists.
GtrLib - Guitar Chords - A vast and comprehensive library of guitar chords with suggested finger positions for every chord.