Yesterday, I got an important and interesting bug report:
We currently do not support domain unloading in the new debugging code. This means that when a domain is unloaded, we do not free the debugging info. To make things worse, some internal hashtables also contain references to the MonoMethod *'s which will lead to crashes later on.
Freeing the debugging info is not so easy since the debugger may access it at any time, so we need to tell the debugger first. However, I got a really good idea this morning and am currently working on it.