Well, I took the car in to the dealer today (for an oil change and some misc things) and decided to see if I could also get this bluetooth problem addressed. I'd experienced the problems described earlier in this thread numerous times in the past couple of weeks....but of course this morning as I prepared to go to the dealer the thing was working flawlessly, so I expected the "we can't reproduce the problem, come back" response. But I figured what the heck, it can't hurt to ask.
To make a longer story shorter, the end result is that I'm getting the TCU replaced (they need to order the part, so it'll be next week before the actual replacement). The SA said that they were able to find "a few bluetooth related stored error codes" and that this lead them to "a couple of BMW TSBs" which indicated the need for a replacement. I didn't get the actual codes or TSB numbers, but will next week when the replacement work is done.
I was surprised that codes were actually stored on this and that this didn't trigger any service reminders/alerts in the car. But so be it. Fortunately, this work is getting done under warranty as I expect that it'd be a $400 or $500 job between the part, labor, and time for coding. Plus, my car will be going out of warranty in about 6 months and even though I may be picking up the extended warranty, it doesn't cover radio-related things, so this would likely be out of pocket if I were to encounter the problem (and want to get it fixed) later.
For those interested, i'll post another update with the codes and TSB numbers once I have them.