Great advice in this thread. Its all about personal preference, physics and playing style. I play with a VERY heavy picking hand and typical run pretty thick strings (.054, .056 ---.012), so I tend to sacrifice low action. I'll be honest and say I always have run my necks with just a touch of relief and have been under the impression that was the way they should be set. I'll have to try adding relief and see how low I'm able to get away with.