My palate isn't really refined enough to be able to distinguish the actual flavors of different types of smoke in meat. I can smell the difference, but I actually did blind-test myself once and couldn't reliably taste the difference. I'm not a wine sniffer either. :-/
That said, I can tell a "harsh" flavor from a "mild" one, but there's several woods that fall into each category for me. The top of my "harsh" column would be mesquite, then hickory. Oak and pecan fall into the middle, followed by cherry, alder and apple down in the "mild" zone.
I like to match single woods with specific meats, for example hickory with pork shoulder, oak with brisket, pecan with pork ribs and tenderloin, cherry with chicken and alder with fish. The reason I stick with single woods is so I can tell if I like or don't like a combination of meat and smoke - if I mix the smokes and don't like the result, I can't really tell which component of the smoke I didn't like.
Sometimes I will try to "cut" a harsher wood with a milder one, say if I only have hickory and apple for ribs or pecan and apple with chicken. That works pretty well (for the most part), but I don't so it for flavor so much. I also try not to pound the meat with too much smoke, I like to have a constant stream of sweet-smelling bluish smoke coming from the top vent. If the smoke smells good, then it'll probably taste good...but if the smoke smells acrid I might pull some wood out, depending on how crazy I'm feeling. /infopop/emoticons/icon_smile.gif