It seems like there's been a lot of buzz around space repetition on hacker news lately. I've used SRS for learning Japanese with great success, and it would be hard for me to imagine making any progress without it.
The one thing I was missing from most SRS apps was the ability to create note cards, not necessarily in the review schedule, and link them with my cards. There are some concepts like grammar that fit the "note" format, but don't necessarily work as a flashcard. Something like a Zettelkasten + Anki, but with nicer interface like Notion.
So I built an app[0] that does just that with markdown. If that sounds interesting to you, or you've been frustrated with Anki, take look and let me know what you think.