Not sure about the Bluetooth retention as I don't have factory Bluetooth in my Tahoe (mine is a 2007). The HU I bought has Bluetooth in it though, so if your HU has Bluetooth in it, then maybe you won't really need to retain the factory Bluetooth.
I also want to post some information about the products that I used in the install just so that other people would have a chance to if they work or not.
PAC OS-4: This little guy is great. It allowed retention of my factory Bose system (with factory amp), factory XM radio, factory OnStar, and my factory back up camera. The directions came with it were very helpful and it really wasn't too hard to set up. Now, having said that, I did screw my install up and my OS-4 smoked up. I have no idea how I caused this, but I got a new one and now everything works great. I was also able to retain the RAP setting (where the radio stays after you turn the vehicle off, but before you open the drivers side door). I also retained parking sensors and security chimes. My only complaint with this product is that the chime module that comes with it (which controls all security chimes, parking sensors, and the blinker sound) is really annoying. It's just a really loud, obnoxious beep. I definitely prefer the factory chimes, but you lose those when you take out the factory radio. Hopefully, someone will create a different chime module. All in all though, I definitely recommend this product if you have a GM vehicle and plan on retaining a lot of the factory settings.
PAC GMRVD: This allowed retention of my factory LCD screen in the back seats. The wireless head phones still work, and I can play any video (from iPod, microdisk, or DVD) on the front HU screen and the rear LCD screen. This was big for me because I did not want to lose the rear LCD screen and this product worked great.
PAC SWI-PS: This is the steering wheel control adapter that I used. It allowed me to retain all of my factory steering wheel controls. Installation is super easy with the OS-4; everything is pre-wired, so you just connect two ends and that's it. You do have to program the buttons though.
And I think that's all of it. The Pioneer X920BT is a really awesome unit. Tons of features and the iPod/iPhone integration is the best Pioneer has made yet. Thanks for all the help from everyone.