I would do anything for Mellotron, and I am a huge fan of Toontrack and in general waste a lot of money on their shit.
Bought it just for the Mellotron sounds, toontrack never disappoints. The interface was a total surprise, wasn't planning on using it for anything other than a sound bank.
It was apparent after like, two minutes that I had forgotten all the chord spelling I went to college for.
If you want backing tracks for shredding in obscure tonalities/modes this is the place to get it. Fucking awesome.
But yeah, really sharp piece of kit. Great usability. add9, sus 4, loads of inversions... it's all there. Really good for expanding your horizons.