My experience ('09 X5 35d), is that if the iDrive has fully booted up before I try and sync, my blackberry will sync pretty quickly. But when I get in the car, start it, and the phone starts syncing during the iDrive bootup process, it can take a minute or so. I have a BB Pearl 8110.

I think a lot of the problem with the older iDrive is the amount of time it takes for the system to boot up. anything that tries to happen during that time (Bluetooth sync, backup camera, etc) seems to get really delayed.

One tip, unlock the car with the key 30-40 seconds or so before getting in the car and starting it up. iDrive gets a jump on booting up that way, and things come up and sync a lot quicker, and you get the backup camera almost instantly.