Works really well on my Asus Transformer tablet running Honeycomb and pretty well on my Droid running 2.1. On Froyo (and probably gingerbread as well) there appears to be a bug when switching from a landscape interface to a portrait interface; the scaling is wrong and the landscape interface will scroll if you make a vertical touch gesture. I spent a lot of time trying to fix this and am giving up for now; you can force quit the app and restart as a temporary workaround if you need to switch between portrait and landscape. Getting perfect support for tablets + phones + all the different size screens is pretty darn tricky.
There’s also no MIDI yet, and no Gyro support. Multitouch works great in Honeycomb; I don’t have a multitouch capable phone to test it on but if eventual (not sure what the current status is on multitouch in gingerbread webkit) phone support in Gingerbread matches what is in Honeycomb it -should- work fine.
Please try it out and let me know how it goes in the forum!