They do seem to take a while to head or cool. My front seats don't heat up nearly as quickly as the back seats do; because in the back the heating element is right under the leather. You may have to clean the filters periodically (apparently they are very expensive to replace) but it's a more subtle effect.
I actually did this last year. I ended up building a custom wiring harness to connect to the car's stereo system. It was a lot of work but I really like having it. A company here in the US has started offering adapters to the Lexus/Toyota wiring harness for Parrot kits. I haven't used one but it might be worth contacting them:http://www.parrotkits.com. I think you may have to wire an external speaker.
Here's the link to my writeup in the US forums....maybe you will find it useful.
The Parrot 3200 is a great kit; although you may want to place the microphone closer to your face than I did..sometimes people say I sound a little muffled on the phone.
Good luck!
