Very cool setups guys. How did i miss this thread until now? I use a 3g ATT 1st generation model, and though i don't do any serious offloading, mostly (paved) road trips, i find the ATT GPS chip to work great. I even have actual 3G service sometimes (pun intended). I'm addicted to all of the fun travel/GPS apps available, but the most reliable is the $50ish Copilot one. I find MotionX to be pretty great too, but didn't want to pay a monthly subscription fee forever. If i know where i am, i usually leave Google (Apple) maps up and keep my music player scrolled across the bottom. Here's my setup.
I have no use for my rearview mirror in my van since i'm used to driving an 18 wheeler and not having one, and there are usually reflectix inserts in my rear windows. I'm hoping to build a mount for mine in place (perhaps hanging from) my rear view mirror. I don't like the distraction of having it so low. I mounted a CD changer control on my rear view years ago and realized how much safer it was to glance over at eye level to adjust things, where your peripheral vision is still out of the windshield. MUCH safer, give it a try! Also, the iPad has a vast range of brightness (dim to bright) so you can adjust it for night driving and it wouldn't be a huge distraction.
It's the ultimate GPS unit in my opinion.