I would agree that Joel Etchen is great to deal with (as is Cole's), if you are buying new or recent make guns. But it is selling vintage guns that tests a vendor's character.
This is a tough subject - YMMV and there are some folks named here that I won't deal with again. KK, you may have phrased it the best way possible in asking who we ar "most comfortable" dealing with, because I am not sure I can say I fully trust any dealers. The two dealers I am most comfortable with are Graham Mackinlay and Francis Lovel - they are both in the UK so you better trust them because returning a gun to them is not really an option.