A 40-50" (diagonal) "whiteboard" is still very small. I have a 4'x10' whiteboard right behind me, and a 6'x4' to my immediate right, and I'm always running out of room.
I'd imagine you can be more precise digitally. And hopefully can swipe around a larger canvas to make more room or something.
Since moving back to engineering work I've started using it for talks, brainstorming and architecture reviews. Eg, this is what a solo few days of project planning & brainstorming looked like recently - https://josephg.com/mischief.png . But in meetings it lacks multiplayer - only one person can hold the tablet at a time, and the interface is nowhere near as intuitive as a real whiteboard. The software is also kind of awful - it idles on 5% CPU usage for no apparent reason, and I've lost work on numerous occasions from it crashing without autosaving (!!). The mac version feels like a bad port of a windows program.
The tool itself frustrates me enough that I'll probably end up writing a collaborative online version on top of sharejs, even if I'm the only person who uses it. (It'd be much easier to do now that pointer events[2] are being supported in more browsers. Safari developers - hate the API all you like, but we really need an interface for tablets somehow!)
[1] https://www.madewithmischief.com/ [2] http://caniuse.com/#feat=pointer