Palm Treo (THB Bury) car kits - any experience?

It's come to my notice that the Palm Store are now selling a couple of
fixed hads-free car kits for the Palm Treo 680 smartphone.

http://preview.tinyurl.com/356bcf

These are apparently proper car kits with power and aerial connections and
a microphone and speaker, not just bluetooth jobbies. They're not made by
Palm, but by someone called THB Bury.

Does anyone here have any experience with these? In particular, can anyone
say whether a Treo in one of these kits will work anything like as well as
a Nokia 6310i in a CARK91?

I assume I'm right in thinking that there is no standardization of signals
for fixed car kits, and that if I side-grade my 6310i for a Treo I will
have to replace the whole car kit and not just the cradle?

Cheers,
Daniel.