I don't think it's the hardware causing the issues, since you can clearly see that things get less stable progressing through firmware.
Anyway, if we don't get any extra functionality, that's fine, but the v20 firmware definitely feels unstable. Really, that's all I care about at this point. I've stopped at RC3, since with my current console (front-loader NES), it behaves properly. Everything later doesn't, which has to indicate some changes made that impacts how well it runs on various systems. (For instance, the weird screen-tearing I was seeing in Ultima IV shows up on two of my systems, and on one it doesn't. Then there's games like Batman which outright freeze, very quickly.)
That's why I proposed that KRIKzz open-source the firmware. If the hardware has already been cloned, and the device is effectively being discontinued with no more work on it, then what's the harm of letting someone else take a crack at getting it more stable? I appreciate all the work KRIKzz has done on it (and I know it's a lot!), so don't let it go to waste!