Edit: As I finally was pissed off enough to write that it automagically started to work and actually mine. The other main issue I am seeing is once it finally decides to mine it works fine. It is only at startup and when switching coins, making MM almost useless in a multi mine perspective that it fails over and over again.
It's really tough to say, especially with issues that are difficult to reproduce. One user did report success in migrating his rigs from cgminer to bfgminer by basically ditching all of his previous arguments and tuning things from scratch.