It's great for learning the Ham radio test answers (publicly available), Major System, and NATO Phonetic Alphabet. I did not particularly enjoy Anki when I first tried it for Japanese-learning. I also found using it on my phone (AnkiDroid from F-Droid) worked better since I could grind it out anywhere I was. I never used their sync thing, IIRC it's proprietary. I also had success once using it to study for a technical interview (tech support, not programming, mostly shell commands and important paths).

I stopped using it a couple phones ago when the app seemed to break after trying to copy over my data. I've had several incidences since where I regretted not knowing the Major System well anymore, as I ran into a long number it'd be useful to memorize for a bit. I mostly used public decks I downloaded, though I did make my own for the interview study.