Their stuff is not great. I've experienced their mirror caps, hood vents and reflectors.
The mirror caps are
FUCKING AWFUL . Although they look pretty good out of the box and match the roof pretty well, their clear coat won't last more than a month or two. It will bubble and warp, and the carbon fiber beneath will become hazy and fade. Autotechnik and the vendor I used refused to replace the mirrors or do anything about the issue.
The hood vents have held up well, and I'm pretty happy with them. I do wish they were a little shinier to better match the roof, I'm considering giving them a coat of clear lacquer.
The reflectors I have mixed feelings about. They have held up fine too, but their fitment is not great (the corners will stick up a bit). If you don't mind using an adhesive to keep them down, though, they look good. Be careful with the 1x1 carbon fiber weave. While you can get away with matching the 1x1 roof with 2x2 pieces because the oblique angle, razor sharp craftsmanship, and thick high-gloss clear coat makes the roof's weave deceptive. On parts that you're looking at dead on, like splitters and reflectors, the difference in the weave is dead obvious.
They do have one big advantage, though, and that is that they are less than half the thickness of the OEM reflectors, so they are a lot more flush to the bumper once you get them fitted. I hate painted reflectors because they stick out so much that they always catch the light differently than the bumper itself and look like patches. Only dark, rich colors like black or interlagos blue can pull them off, the lighter cars look like they are trying to cover something up and end up just drawing more attention to it. However, with the much lower profile of Autotechnik's reflectors, if you were to paint them your bumper's color, they should look much nicer than the painted factory reflectors. I have to get my bumper sprayed anyway, so I'm about to just pull the trigger on getting the reflectors filled.