There has been some discussion in various threads about portable SATNAVs and the downside of suction cup mounts.

Here's what I have- A Brodit clip and Proclip mounting device to hold my TomTom Go 700. The clip is custom fit to the E46 3 series (and can be ordered to fit a bunch of other makes/models). To this you attach a swivel plate and to that you attach the mounting shoe that comes with the TomTom so you can use the hands free mike for your Bluetooth phone. The speaker in the TTG700 is excellent.

I like this arangement better than the suction cup for the following reasons:
I have an easier time working the touchscreen commands because the unit is closer to both my hands and line of sight.

The unit is off the window- it's more secure, especially when it's cold and the silicone (?) suction cup thingy isn't pliable enough to hold a seal and there's no unsightly sucker marks on the window. It's closer to the lighter plug so if I want to use the power cord for longer trips (the battery lasts 4 hrs), there isn't a whole bunch of cord dangling everywhere.

I had concerns the clip would block airflow but there is enough space there so that I get good airflow to the drivers side and I can still work the adjustment wheel in the center. There is ample clearance for the CD unit and I can see all the display screen on the radio.

When parked, I can take the Tom Tom GO unit off the shoe and store it out of site in my just installed Euro first aid boxes received last week from Andy at LeatherZ, or I can take the mounting shoe off with thumbscrew for a cleaner look, leaving just the clip. or I can take the whole thing off-it's not a permanent install so would be good for lease owners.

The ProClip comes for all makes of portable SATNAVS and you have a choice of Brodit clips top go on either side vents (left or right hand drive) or the center vent like I have or along the center console.