The iPhone has more features than your average multiplex, but one’s gotten rather short shrift at the time of launch, and that’s Bluetooth. As Mr. Frakes already mentioned, Apple didn’t bundle in support for the A2DP protocol that would allow for wireless streaming of music; in fact, it seems like the only thing they do allow you to do is pair a headset and even that hasn’t gotten a ton of attention, as it appears that Apple’s own Bluetooth headset didn’t make it in time for the iPhone’s launch.
I currently have a Motorola HS805 headset that I’m not exactly in love with, but it gets the job done. Setting it up with the iPhone isn’t too tricky. Set your Bluetooth headset to discoverable mode first, as per its instructions, then navigate to Settings -> General -> Bluetooth on your iPhone and flick the slider to On. The phone will start searching for compatible devices, and your headset should show up. It may prompt you for a PIN, which again, you’ll have to look up in your headset’s documentations.
Once you’ve got your headset paired, the “Speaker” panel during a call will turn into an audio sources button (or, well, maybe; it worked for me before, but it’s getting tetchy now). Clicking on it will give you the option to shift the audio between your headset, the iPhone’s ear speaker, and the speakerphone. Simple.
I also decided to try and pair my iPhone with my MacBook to see if I could wirelessly sync my contacts via Bluetooth. The short answer? Not so much. The iPhone will pair, but there are no services available to the Mac.

And, on top of that, it doesn’t even show you an icon of the iPhone itself—very unlike Apple to overlook a detail like that. Hopefully, wireless syncing (at least of contacts/calendar) will come in a future update, but for now, you’re stuck with iTunes.
Can you browse bluetooth device using a menu applet? I don't yet have an iPhone, but I'm wondering if you can send files to the device. That would enable you to send ringtones.
You don't mention what build of Mac OS X you are running on your MacBook.
Does Leopard give the same result as Tiger with iPhone?
@David: Nope, no sending files to the device. As far as I can tell there is no place on the phone where the file system is "exposed." No open/save dialog boxes, no ability to access files of any kind except media files through the standard apps.
@Rich: As Leopard isn't out yet, we can't speak to its compatibility. I'm running OS X 10.4.10, as required by the iPhone.
Yeah, I tried to send contact info from my old Razr to the new iPhone. It recognized the Razr and connected to it but wouldn't accept anything from it at all.
I used my Motorola something (I'm horrible with model numbers) Bluetooth headset today and it worked just fine. Once I got the thing dialed.... Thank goodness for red lights.
~C
I suspected as much, but I just thought I'd mention it. Happy iPhoning.
Can you please tell me how many simultaneous bluetooth connections the iPhone supports? Most (old) phones supports just 1, new smartphones now 2 or 3, but i'd be curious to see if the iPhone can go up to 7.
Thank you
Cla