Yes, you can update without buying new maps. Ours also adds the latest speed camera intelligence, too, which is handy.
The worst thing with mine is the way every so often the suction pad fails to suck and falls off, generally at a complicated stage in the journey. The more recent models are lighter, so it probably doesn't happen as often!

Oh - and another feature I really, really like is the way it gives you a fairly accurate ETA and exactly how many miles you still have to travel. Great for the journey home, when I call my husband and can tell him what time to put the kettle on.

Anne