So this thing isn't bad per se, but be aware that:
1: It is not center-negative. Thomann actually says this on the product page, but if you're inattentive (like me), it's easy to miss. This can easily be remedied with a polarity inverter.
2: It is not a Thomann-branded product. Not sure why they claim it is - it's actually made by Goobay. Thomann has brand recognition and is in my experience dependable, so this is a pretty odd choice, since...
3: ... this PSU is not universally compatible with standard effect pedals. It works well with some pedals, but not all - it can cause a nasty, high-pitched pulsating noise to come through pedals what otherwise aren't faulty. In this case, I tried it with two different analog compressors - one functioned as normal, the other one didn't.
TL;DR: It isn't broken, but whether or not it will work with your gear is up to chance.