Personally, I hate suction mounts and feel they should be banned from car windscreens. The windscreen for looking out of - and anything which obscures that view out onto the road should be avoided. Now, having tax discs etc in the corner tend to be quite small - but even so, they should be placed in a position which won't obscure the view of the road. With sat-nav's, I frequently see them slap bang in the centre of the window - blocking a large proportion of the middle of the wind screen. I've even seen a number of them which were placed directly above the steering wheel - right where the driver should be looking!
Sat-navs should be an aid to driving - but not a distraction. Their voice directions should be sufficient for most directions with occasional glancing at the actual map to give context. To need it within your continual field of view is excessive.
Brodit produce a range of clips for each vehicle, typically having a clip low down near the gear stick area, and clips higher up, on the vents both centre and at the sides near the wing mirrors. Whilst I would agree that the lower clips are too low for sat-nav use, the higher ones on the vents are ideal. Typically they're higher up than the speedo - so don't require much time to glance at - yet are outside the wind screen area giving you the full view the vehicle was designed for.
Anyway - the Brodit mounts are brilliant - good quality and hold the phone very safely. I've used them for my Vario and Vario III and been very impressed. No wobble or movement at all when driving, and because it looks (and is) a simple phone holder, it doesn't draw attention of the thieves who see a suction cup mark and think it'll be in the glove box (which people probable still do).
I've used Brodit clips in a Peugeot 306 and a Ford Focus and have always been able to find an option which was sufficiently high that it could be glanced at quickly, without obscuring the view of the road.