I for one am excited that they are attempting anything composition related on a mobile platform. The port of Z3TA is great, but I would love a full compositional song writing tool. I'm a huge fan the iPad (or just tablets in general) as it had opened up a word of possibilities for me with both writing and live perform. If Momentum is half as good as Xewton Music Studio and somehow integrates with Sonar I'll be hella excited. I've written a ton of stuff in Music Studio while traveling but it's still a PITA to get it exported, import it as MIDI, clean up the tracks, transpose stuff...on and on it goes. It's understandable if you can't load a Sonar project one-for-one on an iPad, but having general project file compatibility for the basics (say minus 3rd party plugins or other heavy lifting stuff) would be amazeballz!
I just hope it's not a repeat or v2 of ScratchPad...the world needs another loop builder like I need herpes.