For what it's worth...
I recon the Beemers do come with some sort of electric heater to help warm up the windscreen. My E82 defrosted the windscreen pretty quickly this morning (it was -5.5c).
My old E34 also had a feature where by you could set a time and it would start defrosting the windscreen (for around 15 minutes). So, I would set it 15 minutes before I would leave the house.
There's also talk of coding this feature on the Onesie (see http://www.babybmw.net/viewtopic.php...43036&start=60
on page 5). The explanation is that the feature is disabled for certain markets.
Anyway, I'm gonna talk to my indi to see if they know about it.