I smoked some of the best pork butt I've ever tasted yesterday. Here's a picture of the reason why, thin blue smoke. Big hickory tree in the background.
So, did you use hickory for the smoke? I've been using apple and pear wood, which works well for me. I seem to want to use more smoke chips than I should, but the apple and pear wood make a mild tasting smoke that gives me more leeway than hickory.