To answer your questions, the nav system, fuel mileage and hybrid displays work exactly as they should, it does indeed charge the iPod while it's plugged in and if I needed another one, I would buy it again.

If it's installed under the passenger seat and plugged into CD changer end of the cable, it will not interfere with the nav/fuel mileage/powertrain displays at all. Your dealer is partially right, though. The only way it will block the engine data is if it's installed incorrectly by plugging it directly into the back of the head unit, which is an easy enough mistake to make.

For me, the glitches are entirely tolerable. The CDDJ error messages only appear when my iPod is not plugged in, only appear occasionally and I'm usually paying more attention to the road than the nav screen. As for switching to the wrong track, I think the problem arose when I tried to use the shuffle feature on the head unit and it couldn't figure out how many tracks were in that playlist, so it assumed 99 tracks and started screwing up. If it tries to switch to a non-existant track, the iPod just goes back to the main menu. Again, not a big deal to me.