[Motorola Droid RAZR] acslam:
1. I actually have the pioneer deh-p6200bt in one of my cars - and it doesn't stream bluetooth audio, only phone functions. My other vehicle has a deck which can stream BT audio, and it's great for some things, like pandora, but with my internal music collection the audio quality is just not up to par, it's an obvious weak link.

2. The USB port charges at standard USB rates. It isn't a quick charge but it's certainly enough to make things worthwhile. I've found that on extended, 6-10 hour drives, running pandora, wifi tether, nav, torque and leaving the screen on constantly, yes, it can discharge to the point where it shuts off. I was running this configuration while driving for a touring band once. More often, however, I'm not using everything at once, and i turn the screen off just because I don't always need it. It seems that I can run pandora, nav, torque, and have the phone still actually charge, it was serving wifi tether to the rest of the van that caused the phone to go over the edge and actually pull more power than it wAas getting in. Moreover, the bigger problem I wind up having is that phones will actually stop charging themselves from overheating (sun heat through windshield, and/or just to much load on the phones systems at once), at which point the amperage is irrelevant. In fact this may have been the ONLY problem I was having, while driving I couldn't pay enough attention to the phone to figure out much other than "oh hell it shut off cause its cooking itself".

3. Yes, I want control over tracks from front of deck, and USB is THE most complete way to do that, especially in the one car I have where i have steering wheel controls. I can search for specific tracks from the wheel, as well as call up any phone functions, which is more than the BT side would be able to do - in BT audio mode my systems seem to only be able to start/pause and track forward/reverse. Having hardware buttons that handle both phone and music leaves the screen of the device free for torque or maps.

4. On the audio quality note, if you're playing digital files stored on the device, nothing beats using the stereo to play them via USB, because the deck itself is the actual computer doing the conversion and the D/A converters in the deck should theoretically be nicer than anything in a cell phone. Its the cleanest path one could have.

For things like pandora, this isn't always possible, and in that case the next best option would be a toss up between BT and the 3.5mm jack, based on your ears which is cleaner. in absolutely ideal scenarios, where BT on the deck supports the more recent high quality a2dp codecs, BT can sound as good or better than the cable. A2DP audio isn't exactly this clear cut though, as the blanket of A2DP doesn't specify which codecs are supported, and the better ones are a more recent thing. I'll say that the cell phones have been good about this, it's more that the decks themselves don't always have the newer codecs. And in addition to that, there's still the matter of settings within either device, such at bitpool on the phone, that can have an effect on the sound. Unfortunately, my setup is such that only one deck I have does actual BT streaming, and while nice for some things definitely doesn't sound as good as when it is cabled or using USB directly.

The cable has the disadvantage of running through multiple conversions - the phone goes from D to A through it's own, lower quality converter, the stereo gets that signal as A, changes it to D in order to apply EQ/etc, then back to A as it goes down to the amps. It's generally unnecessary to do something like this if one can avoid it.

There is a third option, but this is very rare and just sort of coming to market - if you happen to have an in car video system with an HDMI input, it will send the streaming audio info as a pure digital signal and as with USB the radios D/A converters will be the units making the actual sound and thus being just as clean. An example of a unit like this is the Pioneer SPh-da100 (I could be wrong on model number), AKA the "appradio2". These are rare, and the least expensive version of this I've found is around 300-350 bucks. One thing I don't like about the appradio is that it seems to have only 2 sets of preamp outs....other than that, it looks like an amazing solution for at least one of my problems!

Basically.... sorry about the confused ramblings. I'm still trying to figure this out. The funny thing is - the phone presents the two storages, internal and external, and both of my radios make the connection - however one radio, a Dual unit, actually sees the external partition first and works fine, while the pioneer radio actually sees the internal first and it gives me nothing! the third vehicle I have, I actually am just using the 3.5mm in for sheer simplicity, it's an old crappy car that has no use for such a nice setup and the moto car dock with the combo usb/audio cable is actually a perfect fit for it. For the other cars, the moto car dock actually sucks, because it won't pass USB data, but that's another issue for another thread. Most likely I'm gonna gut it's frame and insert a straight through USB data cable for it.......

But I still need some way to make the phone consistently present the right info, all the time, every time!