1 day and 10 hours before the PC release on Steam
Oh yeah, it releases later in the UK and Europe. Not sure why. You're going to enjoy it.
The new lessons even have things like teaching you how to restring a guitar, or teaching you the basics about different guitar equipment (haven't watched that one yet, but I'm assuming amps, pedals etc). The technique lessons have a small test, and there are multiple levels for each technique (chords 101, chords 201, chords 301, chords 401 ...)
Menus and load times are vastly improved. Songs load really quick, so you get more playtime rather than sitting and watching load screens and f'ing around with menus.
They've done away with the "event" driven design, where you had to play shows. At least it seems that way. You're now assigned missions, based on what you've just done or accomplished. A mission might be to play a song with a particular tuning, or a song from a certain year. It could also be to try a specific guitarcade game, or to play riff repeater for a certain song.
You can sort through the songs in a variety of ways now, and they will recommend tracks to you based on what you've been playing so you experience a variety of styles. You can pick whether you want to be a lead or rhythm guitarist, and that will give you a different tab to play. You can switch very quickly before you start the song, if you want to do a variety of lead and rhythm playing.
I'm really not good enough to give any useful review of the session mode, but it seems neat.