I can't remember the last time I crashed VirtualBox, browsing or not. Even with older 64-bit Flash. Only issue I recall is some snapshot breakage a while back.
Yay anecdotes.
Seconded. It's never crashed for me, I love it.
I had a lot of instability until I upgraded to a newer vm kernel.
I was on 2.6.38 fedora 64bit vm and it would crash once a day
now I am on 2.6.40 and it has been stable for 50 days