Hey Matt, I would ask question on how they started in the field and why. I would then ask some questions that you do not really see the good one getting asked such as what do they think makes a good design, their process and also what designs do they really like at the moment.

Also I would ask some thing relevant to the technology be it CSS, Javascript etc such as what is your opinion on oprea suing microsoft or what do they think of CSS frameworks.
Try and get a good response out of them.