I bought this to replace a Plantronics bluetooth headset - the over-ear loop contiually breaks and I find them uncomfortable - so I thought the Nokia carkit looked ideal.
The Nokia product has a large speaker and very simple controls, but don't write it off as not being 'gadgety' enough. You don't need mega-functionality with these devices when you're driving, you need simplicity and ease of use. I pair mine with a Blackberry 8820 and a Nokia 6021 - no problems. When I get back into the car I just hold down the dial button on the Nokia unit and it pairs with both devices instantly.
Nokia supply an in car power adaptor only, which was fine for me (although I did a first charge from a mains adpator, so that I could play with it before fitting into my car, which took 10 seconds).
Voice tags work perfectly and I didn't have to rerecord any of them. The speaker volume is loud and I can hear perfectly over town, country and motorway levels of noise. The microphone is good and none of the people I have spoken to have noticed an issue with volume or echo.
The unit is more expensive than others on the market, but I have not had the problems of lack of speaker volume and microphone echo that other cheaper units suffer from.
I compared this product to Motorola's T505, but prefered the Nokia product with it's own built in speaker as I find that FM reception varies as you travel around the country depending on the local radio stations and retuning whilst on a call is not an option.