There's really nothing to say about the best liquor store in town other than it's the best place in town for liquor! They have an inmense selection of wine and beer (although I dare say you can find cheaper wine at Fresh and Easy and Trader Joe's) and most important, liquor.
They have an enormous selection of liquor, divided by spirits. Gin, whiskey, tequila, vodka, etc. They also have an incredible selection of mixers and liqueurs. I have a collection of four cocktail books and I really have to go out of my way to not find something here.
I agree that the customer service could be improved, however I usually come in knowing what I want and where to find it so it does not affect me much.
What would be really cool is if they dedicated a bit more space to glasses and barware. I have been looking for champagne coupes and there is a place downtown that sells really delicate, pretty ones but you have to buy a set of 80 from them (I believe they supply the cocktails bars in town). Othen than that, they get five stars from me!