Well I really think the design of the site looks great, but since you are looking for constructive criticism I will give my input, and I would like to note that most of these are real small and picky things that could just be a personal preference.
The home page slider seems to rotate a little fast for me even though I know it can be user controlled. Also the kerning on your text boxes below feels a little too wide to be comfortable to read since it’s almost as wide as the spaces between words. Also the padding seems to bee uneven on the right box. Just looked at that code and saw you did it all with a p tag…. I would change this out to a unordered list.
On the services page I don’t even think there is much need for another menu, I think you have your services laid out really well as is. The only thing on this page I would change is make your line-height consistent with the rest of your site, and some of your text could use more margins.
The about page I would also bring your kerning down a bit to make more readable.
Like I said, super super picky and minor stuff, just thought I would help out. But the main design of the site as a whole is looking great.