As for the on-screen KB on Ubuntu, I can't say for certain.[/QUOTE]
There are a Ccouple keyboard issues The main annoying one is that Onboard the built in screentap keyboard needsto becset to always on top to be usable in the Unity desktop search field.
Handwriting recognition is OK letter by letter with Cellwriter, easily downloaded from the Ubuntu software repositories :)
MyScript Stylus attempts to provide Windows 7 type handwriting recognition but so far seems slow. It is also proprietary.
However, I have only used it about 5 hours of screen time and it is improving as it learns my handwriting [I'm using a trial version ]
I am not sure I will buy it yet