The blackberry unit was really slick. I couldn't think of it being any slicker....the problem for me was the audio quality. I can't remember specifically, but I had seen this unit (the Giffen) and something turned me off of it.
In my mind, there's 2 key aspects that need to be handled. The first is the audio quality. I quite frankly found reports for the blackberry unit where people said the quality was great. I found this to be untrue when I bought 2 units. (which BB graciously refunded without issue). The second is the integration with the BMWs integral handsfree handling. The car does this wonderfully by itself. The belkin unit isn't as good as the BB unit. I don't have any info on the Griffen unit on either of these, but the write up seems to indicate that you have to hit a button to handle phone calls. The Belkin has this problem too, although its easily within reach depending on where it's mounted. This may not be as easy with the Giffen unit since it needs to plug into the cigarette lighter.