I prefer rugged, but not too much facial hair. Stubble is fine. I've noticed that when my guy's clean-shaven, it actually looks like he's wearing makeup, oddly enough...I still can't figure out exactly what it is that's so different. Maybe his lips look more pink since there's no facial hair casting a shadow on his lips lol.
Sort of in between or neither... like the clean shaven look I picture Norman Bates (from American Psycho) which is bad. Too neat and put together I find unappealing in a guy. But rugged, I imagine some bearded guy like Iron & Wine or Paul Baribeau. Which is usually unappealing, (although actually I find Paul Baribeau kinda attractive, so maybe only part of the time?). I think the guy from Bon Iver has got the "rugged" look down pat: link
But really, it depends on the guy and their personal style. Some look better clean shaven, some look better rugged.
As long as you stay somewhere between metrosexual and lumberjack, you're good.
Also, sorry for the music/movies references, it was the only example I could think of, do a google image search if you don't know what they look like...