I like the design, it is the vogue right now of lots of white space and is not overburdened with graphics. Also, I like the unobtrusive menu bar and I had no navigation issues with a quick look around the site.
Following Simon-Mc's suggestion about about the testimonials, you may wish to sprinkle them around the site instead of (or in addition to) have a dedicated page. You could even randomize it in the banner or something. This would give you additional credibility and might give people a broader idea of the services you perform. Sometimes people lack imagination and, because you do a little bit of everything, they aren't as likely to come to you to fulfill a specific and immediate need.