Ok, since I don't really know where is the best place to
give impressions I'll hijack this thread.

Please do take it as my opinion ONLY.

From my point of view - if it's standalone application
1) There are features that matter most - "Do some drawing" and "Grafitti wal"
- all others can be hidden under "Options" menu.

2) When drawing - I can see that buttons are "smart" ie. they
are not pressed during stroke over them so maybe if You detect
that stroke is being drawn on them - they could vanish until the end
of sketching over them.
Since there is not much drawing tools maybe would fun to have
buttons off-screen - called by some HW (but please not "menu" since
on n810 to operate this slided out keyboard is required). Or some tab "buttons"
leading to full - current button view.

3) I understand that in normal paper usage if You draw with a pen
- You don't have eraser but... with pencil - it's obviouse to use that.
I tried to select black colour as an alternative but I've ended up
with "almost black but not so much as the background" colour - so no eraser
for now. Having eraser would let not to implement "undo".

4) Paper size I call myself rather "extensive" user
of Xournal (I do notes on lectures with it - better to say "trying to").
Since handwriting resolution is rather low while writing on glass - I use
zoomed page - paper size I use is A4 format to ease printing.
I see that liqbase crops nicely when presenting on grafitti wall so maybe
extending page size would be possible.
Then there would be need for panning - ie with pressed down Fullscreen button.

5) Just a question about format - PNG is more than OK but would it be hard to
get SVG? This would give much better effect when printing.

Image export is a good move since I wouldn't like put much of my data
to some format that is not readable in any way that on the tablet app
(I've lost too many lecture notes using Memopad+ with it's database system

On the preview there is cam support - would be great if I could take a photo
and do some notes on it.