I Just Upgraded the firmware on my s2 from .320 to .428
Numerous issues have been fixed on the new leaked firmware from sticky keys to call dropping.
plus the new OS has a better overall feel to it. The clicks seem smoother and more softer as compared to the earlier version.
as for the sticky keys at the bottom it seems it really was an os issue as its been a day and they havent been stuck even a single time.
also the theme screen has been changed. goto options >> theme >>
its a totally new look and layout there. the sms and mms icon has been replaced by sms .
also when you compose a new message it shows only 3 options now sms pin and one more.. cant remember it :P
definitely a better OS and a must have upgrade.
for those using unlocked 9550's there is no need to worry as the phone remains unlocked so dont hesitate.. get the upgrade
If you like .428, you'd really like the .428/.436 hybrid. Longer battery life, improved keyboard functioning in landscape are all improvements I've experienced. No cons (so far) and it's been a week