[EDIT] This has been reposted in the F-series board - can a mod delete this thread? 
Received a package from Pioneer customer support this morning...inside was an SD card and some hastily typed instructions.
N.B. This is an update for a UK spec F900BT, so it may not apply to other models or regions...I don't know.
I ran the update at lunchtime, so haven't had much chance to play with it yet. The procedure is pretty simple - insert SD card, turn the unit on, and let it run. The update took about 10 minutes from start to finish. The old software version was 1.000.600 and the new one claims to be 1.001.500 (I think!).
Initial impressions (bearing in mind I've only had half an hour with it so far) -
- The update didn't screw the unit up...not yet anyway! 
- USB playback is now fine in the map screen, with no stuttering.
- Bootup time may be slightly quicker, but not by much. I timed ~35 seconds to show the main menu (still with "system startup in progress" displayed), and about 55 seconds from switch on until the startup message has gone.
- The response when you touch a button may be slightly snappier in some places.
The only downside is the unit now seems to reset the "Master Volume" (under navi settings...sound settings) to full everytime it boots (twice so far), and it forgets whatever you change it back to. However, I haven't tested this much yet, and the unit hasn't been reset since the update, so I may be jumping the gun on this one.
I don't have an iplop so can't test that out, and bluetooth was fine for me before the update, so I can't say if it's improved (assuming it hasn't got worse - I haven't tried it yet!).
Can a mod delete it please?!