The Google Blogoscoped blog has an entry entitled An Inside View From a Google Employee summarizes a very in-depth Something Awful discussion board interview with a developer who claims to work at Google and is currently responsible for the Google Calculator project as his current 20% project. Excerpts from the summary are listed below

• "Nobody keeps track of 20% time with any care whatsoever. It’s assumed that, if a deadline is pressing on your main project, you’ll work on that. If your main project constantly has looming deadlines, it’s time to talk to your manager or your tech lead and tell them that they’re pushing too hard.” Zorba adds that management understands that a programmer can’t be pushed over limits for more than a week at a time.
  
  And: “At Google, the managers and tech leads assume that programmers can manage their own time. If a programmer can’t manage their own time they’re probably not a good fit at Google anyway."

• ZorbaTHut says that Google is mostly C++, Java, and Python (or so he’s been told).

• On how Google goes about staffing a Test Engineer position, Zorba replies: "I don’t know what other teams are like, but on my team everyone owns their own tests and handles their own quality."

• Zorba: "[W]e have one monolithic source control system across the entire company. This lets us link in handy libraries from other projects, and is honestly one of the coolest things about working here – if there’s something common you want, chances are good it’s already been written."

• ZorbaTHut tells us he was assigned on Google Desktop first but didn’t like that much, so he was allowed to switch to working on Google Video. "I actually worked on some neat stuff on Google Video, all of which got cancelled before release. I unfortunately can’t tell you what it was."

• On what kind of info Google employees are allowed to share:
  "If we haven’t announced it publicly, and it’s a project or a coming feature or anything more financially interesting than ’what color are your carpets’, don’t talk about it. End of story".

• "The company’s structure, at least for engineers, is amazingly flat."
  Zorba says the Google hierarchy is just five levels: Programmer - Tech lead - Manager - Department lead - Larry/Sergey/Eric. Google just assumes their workers are competent, Zorba adds.

A lot of this jibes with stuff I've heard from about working at Google from Google employees or second hand from friends of employees. Thus I assume the interviewee is legit and is either an employee or someone with a contact inside the company. If he is an employee, he's probably going to get fired for this if Google's past actions are any indication.