Runs pretty well. It's definitely good in my opinion (no noticeable errors/bugs). It'd be nice if there was an Android/iOS port though.
Maybe not the most accurate emulator, but open-source, compiles on Linux/x86-64, is still maintained, and has some great features (such as debugger or sprite boxing). It's great to see a Genesis emulator for Linux, even though it's limited to x86 and ARM architectures.