Or at least one of them! I just landed Bug 392055, which makes NS_ENSURE_SUCCESS print out the error code if it failed. No more needing to fire up the debugger to figure out why your function is failing when you don’t expect it. This change is for debug builds only though!
See the bug for all the details, but I hope this helps some people debug things a bit faster. Now go rebuild your whole tree since just about every single file depends on the file I modified! :p