So I have had a little time to play around with all the new stuff in Live 9 so here goes. It certainly is not quite as stable as 8 although it is certainly usable I find old sessions or even new ones take longer to load. It has crashed a couple of times when I have been really pushing it.
The new browser is cool although it could use more organisation but that is more down to me than ableton.
The audio to midi function is REALLY cool & works remakably well. It's not so good with samples that are very busy & have a lot of instruments/sounds in them but can provide some interesting results. It fairs better with solo instruments & drum loops that have clear transients. There are 3 modes to choose from, convert harmony, melody or drums to new midi track. Obviously the choice you make depends on the source sample. Depending on which option you choose Live will then assess the sample then put the resulting notes into a midi track along with a suitable instrument to play the result. If you have a drum loop for example it will split the midi notes into hihat, snare, kick etc. & load them into a drum rack. You can make any drum loop your own in a matter of seconds.
The other thing I'm in love with is the Max 4 Live devices it comes with. Max 4 Live is a totally user programmable language that lets the user create there own FX, instruments & sequencers. It comes with a lot of pre made stuff & there is a large community of enthusiasts constantly developing new stuff, most of which is free! Here's a short video about one of the devices that I really like, the monolake granulator...
http://youtu.be/9pn_b7OUO6I