I haven't had a huge amount of time to work on this (despite starting early), hence the lateness of the entry. I've also taken this project as an opportunity to learn a bit of LESS syntax (the LESS source files are included in the project download).
I have to say, I have a lot more respect for web designers having done this. I am more of a logic/code guy, and trying to produce a coherent, sensible design without ripping off too many other message board formats was a challenge. There are some components I am not too happy with (such as the footer and the submit buttons), and some of the post/reply markup could be prettier. However, all in all I'm pretty happy with it as a first attempt.
A zip file of the theme has been appended to my first post and can also be downloaded here:
Ben added on
Should also add, I had intended the site to be responsive, and it mostly is. However, at phone sizes the layout has overlapping elements from my floats (should really make them non-floating block elements at those sizes) and my footer becomes wider than the screen. I think it's something to do with padding and not using a box-model layout.