I picked up a GlobalSat BT-359 (Bluetooth) for the carputer I am putting together and have no issues what so ever with it.
It is fast to update the map (using Iguidance 3) and deadly accurate. Also it is so small you can practically swallow it! I stuck it on the sun roof between the cover and the glass, driving through a thunderstorm with thick clouds, still alive and kicking. Great product.
(of course if it craps out on me in a month, then, well, my opinion may change... but so far so good)
I've owned two BT gps receivers. The first was one of the first Belkin receivers which is a Fortuna rebadge and I would use it with my PDA, but the two did not like each other much. I'm now using a iBlue 737 and it works absolutely beautifully. My carPC has a Belkin BT USB receiver and after pairing the gps receiver and setting up the com port in iGuidance, as soon as I start up iGuidance I have an instant connection.
The unit itself is great. It lasts forever since it puts itself in sleep mode when it doesn't see the presence of a BT signal. I have it hooked up to a 12v source when the car is on anyway, and in this manner I have not had the unit die out.
It's also super accurate and holds a signal well. I have an easier time with it when exposed to the sky, but once it gets the signal, I could throw it under my seat if i wanted and it would hold the signal.