Interview for passport application and time?

Hello everyone!
I am in the process of applying for my UK passport and I'm just wondering if anyone has had any experience with the process. On the website it says that interviews 'may' need to be conducted. How often is this necessary?
Also, what is everyone's experience with turnaround time. I have left it a little late because initially I was going to apply for Right of Abode and then discovered that I am actually eligible for a passport, but I actually sent the docs off to Ottawa for RofA so I am just waiting for them to be returned so I can send them to Washington for passport app. The thing is, I leave on May 8th, which is 6 weeks from tomorrow... yikes! The website says 4-6 weeks, but what is it in reality? (I know they say you shouldn't book travel until you get the visa/passport, but it was such a good deal on the flight I had to jump on it).
Thanks in advance for your own personal stories:)
Kate