well, i had no choice but to put on .450 because with .448 i was having touchscreen issues in BB News Feeds and other BB native apps. That said, i cannot compare the browsing to any previous version as i had .243 or whatever for like two hours then updated to .448, then quickly up to .450 due to the aforementioned problems. But i can tell you that i am not experiencing the second problem.
I do however use the standard 'mobile' facebook website as opposed to the 'touch' version. I find it much faster and far more simpler to use. Works great with the touch aspect of the phone as well.
I do find .450 to be a solid solid OS. out of all three that i used, i am the happiest with .450 outside of the .448 problems. So i recommend you give it another shot before you downgrade. If you know how to reinstall OSs, i suggest you do that before downgrading. If the problem appears again, then downgrade to .448
