It doesn't matter if you do all the error checking in the world, or if you have the most beautiful graphics, if your site or application design isn't usable, it's not going to do well. Get input and advice on usability and user interface issues here.
The font in the navigation doesn't look sharp (as in classy). At that size I personally prefer Arial over Verdana.
You should do a check on the contents of your search box before clearing it. If I type in what I want to search for, click outside the box, then click back inside the box, my search terms are cleared.
Not a fan of having the background colour change half way through the magnifying glass
Wonder if having the search bar slide in from the right might be a better animation than having it grow from the top right corner.
Georgia looks a bit out of place on the "The Q" page, as everything else is sans-serif.
Wondering if the sub-headings under "Give Us A Shout!" should be <h3> rather than <h2> - both topographically & visually they should be less important headers.
Having the "In the news" header on the homepage be the same colour as links, a) doesn't look as good as different colours would and b) made me think the "In the news" was a link.
I'd suggest styling the Submit button on your contact page. You use greyscale in your theme so it doesn't stick out like a sore thumb, but it's still a thumb.
Why no header image on the "The Q" page?
The background colour when you hover over the current page in the navigation needs to be more visible.
On the profile page, don't direct people to "our blog", direct them just to "our site showcase". In my opinion, a blog is something a person does - like a diary. It doesn't seem professional for a company to have a "blog". Keep doing the exact same thing, but call it "recent activities" or "news" or something else - just not blog.
The search should really be in a big and clear box. I managed to find it in about a second, but this is 1 second more than it should have taken; and to other people it might take even longer.
After looking at your CSS to see how you got a drop shadow on the container, and looking at the image, now, whenever I look at the website I can actually see where the image ends on the left-hand side of the container. This might be the smallest nit pick of all time, because if I wasn't looking really hard I wouldn't see it and it might be to do with my monitor.
Background problem is not with photoshop, but with amount of colors and height of the gradient. For example if you make grayscale background with height 200px and color change from #666 to #999, then each color value (#666666, #676767, ...) will be ~ 4px and it becomes even worse when color changes to something close. That's why it looks like that.
The thing that I felt was a little too much was the size of the images under the menu (the apples under portfolio for example) other than that I have no complaints.