Ok Matty, here goes. Now remember that these are my opinions but it's stuff that I've been learning the hard way.
The colour scheme: this is the most distinct thing in this here blog, and in my eyes the most painful. The green just doesn't work. Now you'll say well what does work hot shot? Hmm well the way you can work out what you need in terms of colour schemes, you need to know what complementary, triadic and monochromatic colors. Do a google search and find stuff about the colour (or if you must color) wheel. From here you can determine what works and what doesn't. Then go here:
http://www.fortressdesign.com/color.html
http://www.colorschemer.com/online.html
Ok done all that? Good. Now let's see at some small bits and pieces to tidy the place up. The buttons on the side, the javascript stuff, nice addition, I like them but:
1. Loose the italic, very bad, no real balance to the whole thing.
2. Make them smaller. It will achieve a better feel more professional, believe me.
3. Centre them, they seem a bit too much swaying to the right, another sign that something isn't exactly right in the land of Mat's log :)
Where Matt's log is written, seems a bit like not much effort has been put into that. Either play around with the actual font and then embed them into the image. This is all meant to be something people will remember, the name of your blog, make sure it's crystal and shiney yet subtle and to the point. The colour chosen is also a bit to jarring on that particular background.
Apart from the colour chosen for the bottom where wordpress is proudly put I think it's on it's way. Welcome to wordpress.