My initial information from Stephanie was incorrect. My car will be piked up in Emden on 10/24, not delivered in San Diego on that date. It's now expected to arrive in SD on 11/17. I'll be interested to hear how long it takes for your TT to arrive at your dealer once the ship arrives in SD.

Back on the original thought...
"By "slow" I mean that it [Garmin] would say something like "turn left in 50 meters" when in fact the turn was right in front of you."
That's not unique to any one company. While a "more expensive" GPS literally can use a faster, more powerful processor, and a parallel-channel GPS signal receiver instead of a slower sequential one, it seems like at the "mass market" level they all can't tell the difference between fifty feet, and five hundred. Partly due to slow cheap hardware, partly due to normal error in the GPS system.
I've had Trimble, Garmin, and Google Maps all fumble the ball the same way that way. And a BMW system that placed a diner on the south side of a wide boulevard, when we knew it was very much on the north side.
Whether any of the auto OEM systems claim to use superior hardware is a whole other question. That might require the customers to know, well, math.

The time lag problem is an issue with most GPSs I have used over the years. The loaner Garmin didn't seem particularly bad. The primary problem was that the database was significantly out-of-date. Major changes on the autostrada that had been in place for many months simply were not reflected in the database. I don't expect the database to be real time, but when I switched to the Navigon app on my IPad, the problem went away. I should also mention that my crack navigator who also doubles as my wife continues to be challenged by navigation of any kind.