I've had a problem with wordpress in that I use blog.spam.eggs:8080 as the base url, but when inside my home network I use blog.parrot, as a setup issue causes a connection refused when trying to contact blog.spam.eggs:8080 (this is my fault, but it doesnt affect the problem other than allowing me to discover it!)
So, basically when im on my network, its trying blog.spam.eggs:8080 when it wants blog.parrot, and this was due to the siteurl variable being strictly defined.. Perhaps I missed something somewhere but anyhow;
I managed to get around this by editing get_settings so that when given 'siteurl' it would return 'http://'.$_SERVER['SERVER_NAME'].':'.$_SERVER['SERVER_PORT'].'/'
But it would be nice to see this as an option to set the base url as that variable, as opposed to something static.
Just a thought ;)