I really like I, Mudd. It's a fun episode, and Mudd was a good recurring character. I'll even give it a pass for being one of the many episodes where they confuse an AI to death, because Spock's scene with the two girls has always been a favourite of mine. "I love you, however I hate you".
A Piece of the Action I don't like quite as much. To me it's just one of those "how can we make an episode on the cheap by raiding the costume department" type episodes that doesn't really make sense, although it's still amusing for the silliness factor, as many of those episodes are. Mobster stuff has never appealed to me either.
On a semi-related but not really note, the brunette was the only one of Mudd's women that I thought was hot. Maybe it's because of my aversion to blondes in general, but the other two did nothing for me.