SRS isn't my main method for learning -- I use a variety of other methods. I only use SRS for (independent and disconnected) atomic-type knowledge that I need to drill. My rep loads are generally not onerous, so it's not a problem that necessarily affects me too much.
(Example: I learn through cognitive dissonance so I use it primarily to deprogram certain associations in my head. For instance, the word "oficina" looks like "office" to my English brain, but the word actually means "mechanic's workshop" in Portuguese. Or "pretender", which looks like pretend in English, actually means "intend". SRS helps me drill the Portuguese meaning into my skull. I use SRS to memorize bits of knowledge that don't fit anywhere and that are hard to create a context for.)
I have looked into SuperMemo in the past because I was attracted to the prospect of a general pro-level memorization tool. I use complex pro tools all the time and was not fazed by the learning curve, but I felt the UI was, let's say, overfitted to the creator's personal preferences.
It was a purely emotional decision but I knew I wouldn't use it regularly, and the best SRS tool is one that one would use over one that one would not.