Ran smoothly, but not very accurately. There are a LOT of games that do not play correctly (or in some cases, at all) on ZSNES.

It's relatively easy to get the first 90%, but each 1% after that doubles the difficulty. This is especially true on older machines where the code tended to be hand-written assembly. When working with modernish machines where there's a SDK for C/C++, high level emulation tends to be much easier to accomplish-- and this is why there wasn't anything even remotely resembling accurate for N64 until the last few years. It was only feasible recently.

Gamecube, Wii, Switch, X360, PS3, PS4 -- these are machines that will remain HLE for a long time. Cycle accuracy will be arduous and require CPU resources we likely won't have for a long while.