Summary: I am very leery of using suction cup mounts for a couple of reasons:
1) You have to make sure that the surface on which you mount the suction cup is clean, otherwise the suction may not be effective.
2) It's a little scary having something as heavy as a GPS unit hanging down from your windshield.

Yes, you can mount the suction cup on your dashboard using the adhesive disk that comes with the c330, but the adhesive on that is very strong, so if you change cars, you will need to get a new adhesive disk.

So, this dashboard mount comes in very handy. It needs no adhesive to mount- it uses its own weight along with friction to hold its place. It is compact, so you can move it from car to car- in fact, even take it with you if you are traveling.

It is fairly heavy so it doesn't move from where it's placed under normal driving conditions (though all bets are probably off if you start driving like Mario Andretti).

There really seems to be no other alternative dashboard mount for the Garmin c3x0 GPS units, so it's either this or the suction cup.

On the whole, I would definitely recommend this to anyone who owns the c320, c330 or c340 units.

Summary: I bought this mount because the window suction cup mount is a pain to attach and remove every time you want to use the GPS. This mount works well both in the center console area and on top of the dash. I prefer the center console area as I think it would be less likely to fly around in an accident. In normal driving the mount remains in place by friction very well and is very stable. Only real downside is that the power cord cannot be disconnected and since the Garmin C3x0 has an internal battery, power is not always necessary.

Summary: I must reiterate what other reviewers have said. The mount works so well (even of contoured surfaces that I wouldn't guess it would work on), it's a small wonder. The GPS stayed exactly where I put it, and I must confess that I don't drive gently. Don't doubt whether it works, just buy it if you want to be able to port it from one vehicle to another easily. It is heavy, though.

However, I don't use it in my main vehicle. I'm an engineer, and I'm convinced this thing will fly towards me or the rear passengers if I am rear-ended hard.