What do mean by "stalls"? Does the X5 see the iPhone? Are you talking about the 3G?

I think no difference. You can set how is address book listed in iPhone settings.

There is a new 2.1 update.

Brian5,
The iPhone pairs, I can answer a call and I can dial, but it starts to synchronize the contacts list and after 30 minutes it is still trying to sync. I have fewer than 20 entries so it is not the size of the book. My blackberry has over 600 and no issues. I downloaded v 2.1 iPhone firmware to my 3G iPhone - I will see if that fixes it. If not the X is going into the shop for a camera fault (again), I will have them look at it then.

My iPhone pairs immediately in my e53 without issues.
Sound quality is better than my 700P as well.

Yeah, that's not good but you're not the first to have had that problem. Not sure if that is good or bad :(
One thing that definitely worked for a handful was turning off WiFi while using it in the car. I suggest trying that (if you haven't already).
This is one of the many threads on this "BMW iPhone" subject that you could read through. There might be some other ideas there that you could try.

I wil try turnong off wifi. Version 2.1 dis not make any difference. No problem with my Blackberry Bold, even with wifi on.

I'd love to hear about your experience with the Bold, it isn't released in the US yet.

iPhone (3G) Blackberry Bold
 

So after three days in the shop, I was given the reply Apple and BMW are working to resolve this problem (will not sync). Apparently it is lomited to pre April 2007 production X5's.

As for the Bold it works well with the X5. However the trackball has frozed on me several times - waiting for a replacement unit.

iPhone 3G - software version 2.2 seems to resolve the synchronization issue