We had an open bar at our wedding, set up as a private bar with a dedicated bartender. The rules of the establishment were that the bar opened 30 min before dinner was served and closed 1 hour before the venue closed. All told, that was about 4 hours. The bartender had a menu of maybe 5 specialty cocktails, plus various beers, wine, and standard liquors.
I thought that was about right for us and our guests. Later I found out that a few guests hit the main bar in the main part of the building (we were off to one side) before the ceremony and then again in the 30 min from when the ceremony ended to when our private bar opened. I guess it's good they had that option, but I couldn't help thinking that they would rather leave the area and pay for drinks than spend 30 min of booze-less mingling til they could get free drinks. And that's a pretty depressing thought.
The only dry wedding (dry for religious reasons, also no dancing) I've been to, most of the wedding party and their friends snuck out back where they'd stashed a cooler full of alcohol.