OK, so there is no new open-source 68k softcore. A pretty good software emulator has been around for quite a while even though its CPU emulator isn't 100% bugfree and thus incompatible (yuck!): WinUAE.
Presumably, Tony is doing is best to get the bugs out. However, bugs are normal, and I wouldn't be surprised if the Apollo core also has bugs, too, given that all the mot processors had some issues here and there.
The problems I see with software emulation are not really bugs. Bugs happen, such is life.
The problem I see is inconsistent performance. On eUAE, I see situations where the emulator crawls so slowly it is simply unusable, while a couple of moments later at a different task it runs ahead at light speed. This is simply not acceptable for a good quality of experience.
WinUAE: well, it runs on Windows. I don't have Windows, and I don't pay Microsoft to be able to emuate an Amiga. I already have a perfectly working Os, without spyware, thank you.
Having all flags available for the subsequent instruction to evaluate and executing several such instructions in the same cycle along with the complex address modes available for each of the instruction is something that makes the 68k a few orders of magnitude more complicated than an ARM.
Hard to judge from here. It seems that the Apollo core is an out-of-order design which is necessarily more complicated, and there aren't many people around that know how to design such beasts. So yes, I have no doubt that Gunnar knows his business. I can hardly judge.