I have an active Brodit mount for mine in the closed position. It accepts the phone snugly, so there's no way of using it with the phone open. I didn't even consider the open mount - I don't think it's practical for in-car use.
I've used a number of different SatNav applications on my E90, in the Brodit mount - in closed mode. That's partly because most of them don't actually work (or work well) on the internal screen anyway, partly because I have a mount for using the phone closed, and partly because they're geared up for use with a numeric keypad, not a QWERTY one anyway.
P.S. Just spotted your last question about the headset socket. I have a number of 3.5mm-2.5mm adapters (kept in different vehicles and with my wired headset), all purchased for about £1-£2 on eBay. The tapered style ones fit perfectly well side-by-side with the power, and I use mine to plug the headphone output into my car radios. In combination with the phone's microphone, this makes a reasonable hands free solution for occasional phone calls.