Same experience as Alan, I find it misses a lot of chords on the fast changes.
I much prefer Capo 3 for chord detection.
http://supermegaultragroovy.com/products/capo/
It's mac and iPad only unfortunately, but has a lot of advantages. You can force it to recognise a chord at any point on the track so if it's missed something just click at that place and it will pick it up.
Also has the ability to build tablature (not on iPad yet). it visually displays the frequencies being played at various ranges, so you can drag and drop notes onto the spectrograph and build up the tab for the riffs. You can change string and fret positions at will.
Not really good for play along, but powerful for working out what exactly is being played.