I bought the official Nokia holder, because I bought a non-official one for my last phone (Nokia 5800- which also had satnav build in) and the thing kept shaking so much that if I was doing anything over 10mph it became unreadable. Well, I'm pleased to say I don't have that problem with this phone holder - probably because the arm between the holder and the suction pad is a lot shorter - but all in all its a very good product.
The only (small niggly) thing I would say is that when you put your phone in, its not just a push and click... To put the phone in you've got to slide out 1 side, then slide your phone in, then slide the side back over the phone, and then slide the lock into place so that it stays secure... and then the same process reversed to get the phone out again. Not too much hassle, but don't understand why they couldn't just make this process simpler!