Well at this point you can have open only one "thing" (Web, notepad, document reader) and within that to have open only one "thing". (webpage, scribling doc, text doc).
Onyx works on multitasking and also work is done to port android (natively allowing multitasking). But if and when it will be released... Who knows?...
So, the question is whether take a risk and buy M92 now, or buy PB 912 now or wait until M92 will aquire multitasking.
I decided not to wait and buy M92, last year. M92 has better hardware to PB 912. Besides better workflow (read: interface allowing to work in effitient way), I miss also multitasking.
But still, I am happy with M92. There is not better 10" e-ink for my type of use (reading pdf and scribling in it).