I don't like any of the vent mount style clips either. Here is how I chose to do it in my e36. I used the adheasive disk and the EasyPort mount kit that came with my TomTom. I really like this location because it is very easy to view without looking too far away from the road and it also doesn't obstruct the use of any vents. I have heard from a few that removal of the disk will not harm the dash at all.
When I am not using the TomTom, I can pop the unit out of the bracket, then fold the bracket over and lay it flat. I also have the option of removing the bracket from the disk all together by simply pulling the suction cup off of the disk. That way only the disk remains on the dash.
Keep in mind that I took this photo from a low level. When sitting in the drivers seat, the dash is much lower, so this does not obstruct the view out of the windshiled at all.
