Eric,
I was using apple most of the time until last summer when I took my 18.5 WSM to my Dad's in Missouri (replaced it with a 22.5 WSM) - I was smoking a butt and a brisket and was headed to Lowe's to buy some smoke wood - Dad told me that he had some hickory in his wood pile, so we used that - now I'm hickory exclusively - it seems like it has a much better taste.
A while back, I did try some cherry in brisket and ribs and it seemed to have a slightly bitter taste.
I also quit using water a long time back - I was using sand, but recently have been playing with chunks of stainless steel. My thought is that whatever is in the water pan is primarily a heat sink to minimize temperature swings - water is a pain to handle and discard - my sand occasionally would soak up some grease even though I was double wrapped with aluminum foil - steel makes a nice heat sink that is easily cleaned - stainless is nice because it won't rust.