I have the 6280 with v3.81.
The problems I still get are:
1) Random reboot - can happen anytime, during a call, going to WAP etc
2) Random switch off - again can happen at anytime
3) Will not connect to GPRS - Error saying 'Packet Data Not Available' even in good reception area. Turn phone off/on corrects it.
4) Cannot save words in text dictionary - workaround for this is to 'Insert Word' from the menu. The word then saves for future use.
All of the above happen occationally once maybe twice a week - annoying but not as bad as the previous firmware.
From looking around at the forums it seems Nokia have released a dud phone. Everyone I've spoken to has have problems.
Nice phone tho but if you're buying new, wait for the 6288 and check the forums for firmware bugs!!