[mpf62]

I second that one, plus:

I would especially check up on the persistency of the founders. Are they really dedicated to the product/company or are they going to lose interest if either VC money is used up, they have not become rich after a few months or there are harder times ahead for some other reason?

It usually takes years to build a really cool company/product, so I would make sure that I’m not the only one still putting his best effort into that project after the initial euphoria has faded away and the others are doing not much more than just hanging around … or even worse: start bitching.