I've finally had a reason to go down to London where I had the chance to upgrade my P800's first generation firmware. I had it done in Tottenham at R's Electrics with a two hour turnaround. So far I have noticed a definite improvement in iSync reliability, instead of failing 100% of the time (unless you went through a complicated rigamarole) it only fails about 50% of the time.
I'm still working on improving that, it may be 'interference' caused by BluePhoneElite or Salling Clicker.
Another noticeable change is the default video-player now has a widescreen option to play back video in landscape mode. The default picture viewer also benefits from a new landscape mode. Both huge improvements! The camcorder app also now has a night-shot mode.
Checking my firmware version numbers (in the Applications list, click view and then system info) displays this:
Phone: R2F Bluetooth: R5A Organiser: R2D02 CDA: R2A
I'm not actually sure if this is the very latest firmware or not, but it's several generations ahead of my old firmware. So far so good.