i've upgraded mine but to .52

it was slow at first but after reading all the menus etc. its smooth.
i think 4.5 is like vista on pentium 3 (pearl). but we'll see if RIM will fix it
camera is a big issue right now specially if you want to take a pic and send.

at least the multi-tap issue was fixed

edit: moto ht820 works awesome!
no reboot/freezing yet but I dunno if I want to restart it just to see if it still slows down at start-up.