I'm very sceptical of the ability to do a good, fair "culture" interview; I've never seen a cultural line that divides good hackers from bad, and it's easy to use "didn't fit the culture" as a cover for discrimination.
Project experience you often can't tell about, and passion is a red herring - the best developer I ever worked with was the guy who'd rock up at 11, hung over more often than not, slump in his chair and give every impression of not giving a damn about anything. He still got more done than anyone else, in higher quality, and teaching the rest of the team as he went.