Overall I like it, especially the simple clear navigation, however I would suggest these critiques:
1. Twitter account - As a professional web designer I don't think the twitter feed is relevant at all, the ones I can see at the moment are about xFactor, and your bed, which doesnt sound too professional, so either remove the twitter link and feed, or make some relevant posts?
2. Home page title - I persoanlly don't like the 'welcome to X site' (i'm sure many people do tho) but having some titles in the page instead of that would be better, for example: 'Daryl Summers Portfolio', then also add in more sub headings, like 'Aims&Objectives' - I think many people can be put off by long(ish) paragraphs and content should be minimal and straight to the point.
3. Testimonials - Similar to the point above I think there could be some extracts of the long testimonial that are only 1 sentence long and give a quick snappy positive comment about you.
4. Links - In the about page the links have a very thick black line under them, maybe making them look nicer (more thin, dotted, different colour etc) would be better.
5. Contact - Do people send letters now adays? Maybe the 'Write to me' is a little out of date, seeing there is an instant web form to the left of it... and maybe having a 'subject' in the form would be useful for you when receiving emails.
I like how you laid out the servers and portfolio pages.
Anyway, that's some of my critical feedback- everything I write is not meant to be nasty, but simply constructive, and I hope it helps. In any case, I'm a young graphic designer, not web designer, so just let me know if i'm talking balls
