Brilliant little store. I love the idea of it so much that I pondered investigating what it would take to open my own Vom Fass in San Francisco. Then I remembered I did do retail work (albeit at Shopko... which is a pretty lame store) as a teenager, and I soon realized that wasn't my calling.
There's a lot of unique and amazing oils, vinegars, and liquors. You pick your bottle and fill it up. Bring the bottle back, and fill it up again. It's really nice to be able to buy a small amount of a very expensive bottle of whiskey or whatever.
I went in on two separate occasions and both times there was only one person in the store. Both people were exceptionally friendly and knowledgable.
If you're into food at all, you really ought to go there some time. It's actually fun. It's one of those places that deserves Food Network attention... it's really very unique and interesting.