[chrisss]

I've just started using the MuseScore app for android (https://play.google.com/store/apps/detai...lite&hl=en) and windows (http://musescore.org/en).  
Not fully discovered all the features and would love to hear any comments.

I've used MuseScore for Windows for several years and am really happy with it.  Windows is completely free- open source.  The Android app is like $5. 
Like all notation applications I've used it took me a while to get the hang of the user interface but I think it's the best of the several I've used, including most recently Finale PrintMusic.  It seems to have substantially all the functionality of the big scorewriters (Finale + Sibelius) and of course the huge advantage of being open source + free.

They've just come out with a major version upgrade from 1.3 (I believe) to 2.0.  2.0 is a big step forward - I haven't yet upgraded, but I used a beta of V2 for a while and was pretty pleased with what I saw.

I think the Android app has huge potential, but it seems to me to be relatively low on the maturity curve.  You can't write a score on the Android app- it will play the score, but to me the HUGE advantage is that you can transpose a score live on the fly in MuseScore on Android.  The current version renders it pretty roughly, but as it gets better, this is a game-changer in a jam situation (jazz, folk, etc) when somebody calls a song I sort of know and have on the tab, but they call it in Ab instead of F, or whatever.