An unsuspecting storefront that makes it look like an abandoned store, Acacia is not the place for you if you're looking for luxury and plush seating and an attentive waitstaff. However, if you're looking for the more stellar cocktails in Pittsburgh, for bartenders who are at the top of their game, and a completely unpretentious setting that is reminiscent of hidden bars during Prohibition--this is the place for you.
Amanda and Richard were behind the bar the night we went. The cocktails--some from the menu, but most a result of us saying "I love this, and this, and not sweet, but like this..."--were exceptional. The ingredients they have to work with + their knowledge yields things I've never tasted before. So do yourself a favor, tell them your favorite liquors and flavors (eg citrus, smoky) and let them work their magic.
Sit at the bar, so you can be front row at watching aforementioned magic. Talk to the people around you, ask what their having. Don't go with a big group--there's not room. Be adventurous and try new things!