I move the mount between cars a lot as well, and I find it pretty quick and easy to remove once you unlock the suction thing (it's STRONG!), and there's also a little pull tab to help easily remove it from the dash/windshield.
Here's the review of it that convinced me to buy it: http://www.youtube.com/watch?v=pNbSegA_6Iw&feature=youtube_gdata_player
iOttie link: http://iottie.com/Product/ProductDetail.aspx?ProductID=955&ProductType=321
I absolutely love our iOttie. I'm just going to buy a second one for the other car. I'm waiting to see how it holds up to 40-50 below zero weather here in Minnesota.