Main plus point is that it will accommodate your iPhone (4 in my case, but would also be fine for all models) with or without a case or bumper, with nice soft cushion sides and one handed release and (just about) install. Only had it for a couple of weeks, so can't be sure of durability, but it feels reasonably strong, though would be easy to over tighten the screws (unnecessarily, as only need to be done quite loosely to hold in position). The other potential negative is that the arm isn't very long, so sits quite close to windscreen. Good for lack of vibration (I have a Golf GTi, so quite firm suspension and doesn't vibrate or bounce, despite other reviewer's apparent experience), but possibly an issue for a steeply sloping windscreen, as it could end up being quite away from you. But overall really pleased, especially for low price, which is half or a third of some others I've seen.
12/05/11 - Unfortunately, after around 4 months, the suction cup stopped working, so now item sits redundant in my garage, shame as otherwise worked a treat!