I've used the MTH Product/Dealer Locator on occasion over some number of years with pretty good success. If I'm looking for a particular MTH item, I usually go there first to see who may have the item. If just one dealer is listed, and if that one dealer is someone I believe I can trust, I generally pick up the phone and give him a call. If a number of dealers are listed, I pick the one I know and trust the most (if there is one) and call him to place the order if the price is right.
In short, I use the MTH Dealer Locator as a starting point, realizing full well that there may be other dealers out there who do not list there at all, and also realizing that I may need to expand my search a bit for a particularly elusive item. Dealers who chose not to be part of the Locator or who fail to update their list when new items are released, simply stand a better chance of losing out on the sale because, as I noted, the Dealer Locator is usually the first place I am apt to go.
I have no real gripe with dealers who have neither the time nor inclination to update their listings on a daily basis because I recognize that in some cases that is simply expecting too much. I imagine most of these folks are not techno-geeks, and they are just doing the best they can with limited resources (personnel and $).
And I will say that at least MTH has a Product/Dealer Locator, despite any flaws it may have. It has served me well on a number of occasions.