UDP means that the data stored on the internal memory of your phone should be preserved despite of the firmware update (previously the internal memory was wiped). However we would still recommend a back up either to a PC or to the memory card.
UDP worked well for me with key information from Contacts, Calendar and Web retained. Third party application also remain untouched. I'll report problems, if there are any, in the comment thread.
A bigger firmware update with added support for Flash Lite 3 and WRT seems likely for the N82 in the future.
As usual the firmware update is available for non-operator variants initially.