I installed a Parrot Mki9200 in my
Ibiza last week (with
help from a friend).
It was relatively simple. The most difficult parts were removing the fascia (we used trim tools to prize most of it off, but we couldn't get the top 2 tabs to release. We managed to lift up the fascia and unscrew the headunit with those clips still in, so it didn't cause us too much trouble) and getting an ignition feed, which we took from the cigarette lighter/power socket.
We had to make up some wiring to allow the cars Aux In to still work. We wired in the Mute to the designated pin, but it seems to have no effect. There was plenty of room behind the stereo through some holes for the box and all the wiring to be stowed.
All in all, it was fairly easy. If you've done it before as you say, and you or someone you know has some basic electronics skills, then it shouldn't cause too much trouble.
The Parrot kit is very good. It plays music off my USB stick fine, and we had it connected to an iPhone and it all worked very nicely. When driving it seems to lack a bit of Bass. Tweaking the audio settings helps. It's not a big deal for me anyway.
I can't comment on call quality because I can't get my own phone to work with the kit
.