I really like it, looks professional. I think the homepage is lacking a bit of colour at the moment, but this could be achieved by putting colour logos into the scrolling bit at the bottom that shows each of your projects. I didn't really want to read it as it was all one colour and I think changing that would really help. The only other thing I'd say is that the graphic under the nav bar looks a bit blurry, not sure why.
I agree its very professional looking. Although its simple it is still an effective design. I think though that the logos further down the page should be in colour though...
Professional looking indeed but try to render the header with the 4 guys holding the lego thingy a bit higher quality.