It has worked in almost every game that I've tried on my cart so far. The only game it did hang at, was Contra 4. It hangs at 39%.
But every other game it has worked. I'm sure they will improve on it more and more. TC just said that they will release their RTS in the next few days. And it's not perfect just yet. But that it will improve a little with each update. So I'm sure that's what the Supercard Team is planning on doing too.