I've only had one interview -- it lasted 90 minutes and got me my first junior test engineer gig. They'd already downloaded all of my portfolio apps and looked at the code, so they knew I wasn't totally stupid. The interview merely confirmed this.
I've been fortunate enough to interview a load of people so far for test engineer positions (probably around the 8 mark) and in the first one I was probably as nervous as the candidate, haha. It's tough to do ... there are many bases to cover for programmers, and you really don't want to hire a bad one, so you do your utmost to throw the kitchen sink at them while also giving them the space to demonstrate their knowledge/skills.
Even companies like Microsoft go through turmoil and huge changes in their interview process, and the likes of google apparently have vastly disparate styles of interviews depending on which person/part of the company is conducting the interview. In short, it's a hard problem.