If we're talking about the truly heinous, then I would refrain. Why would I go for 3s or 4s when I know that a slightly above average girl is well within reach?
It's the 8s and 9s I have trouble with, and I'm learning how to get those. I'd say 80% of men (excluding the handsome and very charming or rich/powerful) have problems with these. I'm talking about KEEPING them, not just seducing them for one night or a few weeks.
Anyway -- I guess it differs for people -- the bottom line is that I would never bang a girl who is WAY below my means, but I would hit a girl within or just slightly below my reach, for companionship, human contact (sexual/emotional), and the like. Nothing wrong with that.
But one needs to see that it's different for different people. For example, a guy who is a 4 in looks, probably shouldn't only strive for girls I consider 7s. If that were the case, he would get laid once a century (keep in mind that this can be overcome with major status or wealth).
I honestly think that wealth and status are the NUMBER ONE things that override an ugly outer shell.
Having good looks is the next best thing.
Then (a close third, not too far behind) is personality.