It has very high quality cocktails, and a nice atmosphere.
You don't need to be a member- you need to go to the website, make a reservation, and when you ring the bell at the door give them the password (which is given to you from the website/by email). Very easy, and a little bit different.
Bourbon and Branch also has the library and the smaller room to the right of the main bar. One can always get into the library with the password that is posted on the B&B website. Rickhouse is owned by the same people and has slightly less expensive drinks. I personally prefer B&B.
I thought it was over rated. I liked it but when I saw they were using Smirnoff vodka for the cucumber drink I was a little put off.
Neat place though.
I think vodka is having a Merlot moment (think Sideways) and this place views it as a means to add alcohol and not flavor. I know of at least one fancy cocktail place (Teardrop Lounge in PDX) that will sometimes refuse to make vodka based cocktails. It's all part of the new cruelty.