Seems to work fine, but is there any special reason why the content only uses half the page?

not really, other than the fact that people with pretty much any screen resolution will be able to view it properly...

Hmm, that shouldn't be an issue, since you don't use any graphics... I'm running 1024x768 resolution and it takes approximately half of my screen width. On bigger resolutions, it will probably look really crammed to the side.