Just because Meredith isn't married to Finn, doesn't mean it ain't cheatin'.

But I agree, the Ellis:Richard::Derek:Meredith equation works best. But Meredith has the choice between safe and between soul-searing passion, too.

'Course, I think that's a false dichotomy, and that in real life you go for the wonderful sweet guy who isn't married already, but y'know. I'm just speakin' from hard-won experience here. :)