Just did the update and got all functions back, like track info. Woohoo. About time.
Here's the link to the UK download. I'm in the US and it worked fine on my AVH-P8400BT. You can also download it on the US site but they made it hard to find.
http://www.pioneer.eu/uk/support/software/AVH-P8400BT/page.html
Also, I was able to install it on my unit with my MacBook Pro's Bluetooth Connection even though the instructions don't say how to.
Great! I'm a little surprised you can't do this via SD card but whatever 
.
Yeah I was expecting to just plug in my USB too, but I got it working, so I'm happy with the results. It took some trial and error from my Mac but it worked in the end.
Insane the hoops you have to jump through to do this...
About to attempt it now...
Now that you updated your bluetooth... I modified the newest version of Spotify for Android to display track metadata via Bluetooth like the iPhone currently does... if you use spotify and want metadata on your headunit. Check out this thread on XDA: http://forum.xda-developers.com/showthread.php?p=37404226#post37404226 also uninstall your current version before trying to install the modded version.
The fact that we cant update the unit via USB/SD card is atrocious. I mean seriously, world class company pulling such bullshit.
Yeah I was expecting to just plug in my USB too, but I got it working, so I'm happy with the results. It took some trial and error from my Mac but it worked in the end.
How did you get it to work with your Mac? Any instructions will be greatly appreciated.
Thanks
I can give you mac instructions. But i did do the firmware update and now the iphone will not connect to the unit at all.
Same here, I used a pc and now my phone is not able to connect at all. After transferring the file and on the unit clicked on update bluetooth, it seem to work because it said it was successful. I could not verify the bluetooth version number and now the bluetooth portion of it is not working at all. Not only can I not stream music but I also can not make phone calls.
Planning to call Pioneer on Monday afternoon.
I used a PC and everything went well and it's working great.
Make sure you follow instructions to a T. Maybe try it again? Why couldn't you verify firmware version? Was the source off when you tried to check it?
Can someone post a "How To" using Win 7 for a Novice....?
My Unit was installed yesterday and so far the only connection I can make to the iPhone is via Bluetooth! I can listen to music and the iPhone (5) will charge but no App Mode. I am using the CA-IW.201S iPod/iPhone 4/4S to USB Connection Cable with an Apple Old iPhone to new iPhone connector converter.
I successfully updated a 4400 last night and my 8400 this morning.
As far as app mode goes, according to the table on the pioneer site that is not going to work. For an iphone 5 with the lightning cableblue tooth will work, with the 30 pin adapter you pick up music playing with control and meta data but the video and all the app modes do not work on the 8400. Basic appmode but not advanced will work on a 4400. All of it works with the older 4 / 4S old touch with IOS 6...
I used a PC and everything went well and it's working great.
Make sure you follow instructions to a T. Maybe try it again? Why couldn't you verify firmware version? Was the source off when you tried to check it?
There was a time I jumped a step when my notebook connected with the hands free device I tried to send it instead of dragging and dropping the file to the headset device folder, I rebooked my notebook because I couldn't cancel it, but was able to connect back to the unit and followed the directions line by line and not jumping ahead.
I dragged and dropped the file to the update folder on the handset drive it said that it was completed and even displayed on the screen like the screen shot from page 5. But was unable to see the firmware version. So now it's stuck, I'm unable to select any of the options. It displays Error-10 when enabling the bluetooth option.
I did it according to the instructions but kept getting a message from my laptop stating that the drivers could not be installed. It seemed to transfer the file successfully but when I checked the firmware version it was still showing the old one. Someone that has had success please post step by step instructions.
Thanks
Same here, I used a pc and now my phone is not able to connect at all. After transferring the file and on the unit clicked on update bluetooth, it seem to work because it said it was successful. I could not verify the bluetooth version number and now the bluetooth portion of it is not working at all. Not only can I not stream music but I also can not make phone calls.
Planning to call Pioneer on Monday afternoon.
Which unit do you have? I found a step they seemed to have left out. Once you get the complete on the units screen, turn it off and wait about 30 seconds. Turn the car back on/unit back on (I did the whole update out of the car). Clear the bluetooth memory. Press source so the audio is back on. Press the phone icon. Then press the settings ikon from that screen. Not sure if it was a option before the update but theres a search (magnifying glass) ikon. Press that and it searches for the phone and then press the button your phone to connect to the headunit. This got my iphone back connected to my p8400bh.
Updated succesfuly. 
This is a response I got from Pioneer regarding the BT upgrade failure:
Mr. Clutch,
The instructions for the firmware process are very specific and must be
follow precisely. If any part of the update instructions are not followed,
it will cause failure. Hence, it is not covered, since it is not a
manufacturing defect.
Please send your unit to us at the address listed below:
PIONEER ELECTRONICS
ATTN: ARA 16312704
1925 E DOMINGUEZ ST
LONG BEACH, CA 90810
Once received, we will evaluate the unit. If the $95.00 fee applies, we
will contact you.
Thanks again