After two phone interviews, I was brought in to interview before a panel of developers and software project manager. They were all very helpful and nice, but definitely asked probing questions.
Before the interview began I was given a demonstration of the primary product (InformaCast) that the company produces. It is a very cool product, and is very complicated. One point that most applicants miss when they are brought in is that that demo is part of the interview. They want to see if you're a) paying attention, b) able to ask probing questions- how does this work, how does that work?, c) capable of grasping the complexity of the product after asking a few good questions.
The best advice I can give to prospective interviewees is to try to give the interview team as much information about why you are a good fit for the job and the company. If you don't slip up and reveal anything that isn't harmful to your chances, but at the same time, you don't demonstrate that you are going to be a contributor and a good cultural fit, then you will not stand a chance of getting hired.
Play up your strengths and explain but don't dwell on your deficiencies- if you are a good fit, they will hire you even if you're not perfect.