How does the user preferences table stores the user's preferred stylesheet? Is it just an index number, or does it contain the URI for the stylesheet? If the latter, may I suggest that we allow users to specify the location of a personal style sheet for wikipedia. For example, I could then take the Cologne blue stylesheet, change the things I don't like about it (such as the article text size) and host it on my own webserver*, point to it from my wkipedia preferences, et voila - a fully customized view of wikipedia, but I am actually reducing the load on the wikipedia.org servers by not getting a stylesheet from them.

*actually, I could access it from my PC via file:// protocol, but hosting it on the web gives me a mobile profile that I can use form any computer.