Hiya James. I have no part in KM's future (I use Win98 and understand very little of what goes on around here administratively) but for what it's worth I can offer you my opinion about the basic look of things, focusing on the front page. I apologise in advance if my criticism seems unkind as I have no wish to discourage anyone.
I compared the following three test sites using my default KM on Win98 and with IE7 on Vista:
(Modified August 24, 2010)
(Modified March 13, 2010)
(Modified June 6, 2010)
Screenshots of the Dorian and James versions in each browser: kmx4.jpg
(very large images)
Dorian's header background graphic certainly has some serious issues in IE7, and all sites have small issues in IE7 with the large text (using the H1, H2, etc. tags, which I seem to recall are known to render differently in different browsers).
I won't address the header problem, though I'd suppose it's css related, but I will address the look of the background graphics. I prefer the look of the header in the second screenshot in either image (Dorian/KM) although I'm unclear about how it's displayed compared to how the base image looks (css tricks again I suppose). I know there is also an overlay of a png with alpha channel transparency which gives a gradient shadow effect, which does look good but fails in IE7. So, multiple browser testing will be in order.
James, I'm afraid your header graphic needs to be scrapped, it's too coarse as displayed (too much light/dark contrast for optimum text readability), it shows unpleasant tiling artifacts and has suffered seriously from jpg compression. You are on the right track however, by using a simple image displayed without unnecessary css tricks which can lead to failure like the original header in IE7. An image like Yogi's in the third post in this thread might be the best choice, it has the right color and contrast and smoothness and such. How the transparency overlay might come into play in the final choice I couldn't say.
I am still not sure of the menu system. Black text does not show well on the red background of the original. I have a different background but I kept some red by putting it in a border.
The black on red in the original is horrible, in fact the red on every aspect of the original menu is horrible. Theme be damned, it needs to look good and be very readable. Your textured background on the popup menus is certainly better, and while I understand why you did it I still dislike the red border.
The truth is I like Desga2's menu the best of all, the bold text in the menus definitely looks the best. And yet, while setting the browser to an 800x600 size (a minimum target in my opinion) his menu breaks and wraps, being too long, while yours and Dorian's fit comfortably.
I also think Desga2's horizontal layout of the exe/7z packages looks best, his footer with copyright/sourceforge logo looks best (a minor issue). Worthy of mention is the difference in the rounded edges (or not) of his button in KM vs. IE in my screenshot, more css stuff I'm sure.
Desga's obvious big-button download link looks great to me, the way it sits below the intro and next to the screenshot, pushing the latest news to the 'next' section of the page.
I personally like the look of the original single flag/country drop down menu but having the array of flags as you do looks good and is a nice gesture considering the multi-country effert behind this browser.
Some kind of vertical lines/borders on the sides might be good idea, I'm not sure, but I don't think they're looking good enough as is.
Finally James, earlier you wrote about having larger text but your latest version has the smallest text of all, which is too small in my opinion.
I wish you well, and apologise for being so nitpicky. I drive myself
crazy when I attempt graphical projects like these, and I've learned in the past that I stink as a web designer.