I don't think Addison did anything wrong. I say you go!!! I am normally so opposed to adultery in any story (and, of course, in real life) but in this case, I am so completely on Addison's side, it's not even funny. Based on what we heard the last year of their marriage was like, him ignoring her, treating her less than, etc. (and if last season was any indication, he treated her REALLY shittily!) than as far as I'm concerned, Addison could have slept with every guy in whatever city they were with and I'd STILL be on her side. And absolutely nothing in this episode or the last episode or last season makes me feel any differently. Derek is an ass. Derek ignored her when they were married before. Derek humilated her. Derek chose FUCKING MEREDETH over the utter awesomeness that is Addison, so I say you go for it, Addison! You take McSteamy and anyone else who will treat you like the goddess that you are and you live it up, babe!!!!
I SO need an Addison (Kate Walsh) icon.