Thought I'd chime in with my 2010 nav experience. I LOVE it. Here's the positives:
Sync integration: Being able to voice control the nav unit makes it very easy to use.
Sirius Travel Link integration: I get weather, sports, and fuel prices right on the display. Very handy when low on fuel or to check weather conditions during a trip.
Display: It's an 8" screen. Much easier to see than a smaller PND. Plus if you get the reverse camera it's used as the display instead of the rear view mirror.
Prompts: You can get the navigation prompts through the stereo as opposed to the small speaker on the PND. Some PND's have the ability to connect to the stereo, but then you lose the ability to listen to the stereo at the same time.
Now, things aren't all roses. The voice prompts with the nav unit can be kinda wonky. For example, to place a phone call you have to go into the "Phone" voice menu first then place your call. You can't just hit the voice button and say "Call home". That's the only crazy thing I can think of.
For me, I feel it's worth the price. I've used PND's before and this is the first factory nav I've used.
My .02