I thought about it for a minute, but judging by the number of times my radar detector and GPS have spontaneously popped off my window, I just don't trust suction cups in general - on the window end OR the device end.
A much better idea - I did this as soon as my iPad was delivered on Friday:
1. Buy a reasonably-priced sturdy back shield/cover. I used this:
http://www.handhelditems.com/ipad-crystal-clear-polycarbonate-padshellor-case-clear-black-p-132383.html
2. Get a "Move Clip" System from Proclip (they sell a smaller/cheaper one than this, but I felt safer with this larger model made for "tablet-style devices"):
http://www.proclipusa.com/brodit-device-holder/proclip-move-clip/mounting-plate-for-tablet-style-devices-215159-13975.aspx
3. Attach the female move clip to the back of your shield. I wouldn't rely on the peel-and-stick they give you, though. I used "general purpose cement bond" from the hardware store. Keep in mind which end is "up" before you do your gluing! Note- since the base I was attaching mine to did not have an amps pattern (and I have no patience and didn't want to wait a day to swap it out), I decided to glue the male move clip to my case. I don't recommend this because the female clip does not have holes so I had to drill and countersink my own.
4. Attach the male clip to your favorite tilt/swivel holder (Kuda, proclip, whatever) with standard "Amps Pattern" holes using screws.
5. Now you have a sturdy mount that simply lifts off when you leave the car (or when they are trying to get to your mangled body with the jaws of life because you were driving while watching "Superbad" on your iPad).
6. And, you can always swap your other devices back in.