I have been thinking of getting one for my car. All in all, I've heard nothing but positive reviews, but the thing that puts me off is the prospect of having 3 or 4 cheap, plasticky-looking objects scattered around the cabin (microphone, screen, remote). I suppose it depends on personal taste really, but I'd rather keep things as uncluttered as possible. Think I'll probably end up getting a new head unit with built in Bluetooth/iPod - probably one of the new Sony ones which can Bluetooth stream music as well.
The only negative review I've heard about the parrott is that it can be a bit of a pain trying to upgrade the firmware, but I think that's a given with all of these things.