Mr. Muffins for sure! He generally offers free shipping and a very deep discount on gear. Very fair as well. I pre-ordered the Lionel O&W F3's from him and when they were delivered in that horrible silver color, he offered to either sell them to me at dealer cost or exchange for any other F3 set that wasn't buggered. I am not in the market for a single item this year because space has run out BUT if I were, I would not shop anywhere else.
I agree with others on this site about pricing though. Several times I "just had to have it" so I jumped on the pre-order train but history taught me that after I left the station with my shiny new toy, several dealers offered a better price on leftovers that nobody claimed or overstocks they were left with when the "gem" turned out to be fools gold.