Serving a cached list of articles immediately and updating it after the initial load has happened would make for a better experience than spending a lot of time staring at "Loading...".
Minor gripe with navigation is that the previous list of articles doesn't get cleared when I click on a different category. The experience is: I am looking at the Node.js article list. I click on PHP. I see "Loading..." show up at the top of the Node.js article list. Then "Loading..." disappears from the top of the Node.js article list. Then the Node.js article list is replaced with the PHP article list.
It would be clearer to me that the site is functioning well and realizes I clicked a button if the Node.js article list disappears as soon as I click the PHP link. It can then be replaced with a blank "Loading..." page or, as mentioned above, a cached list of PHP articles and an "Updating..." notification.
Do you plan on taking it in a reddit/HN-like direction with local comments/voting?
A programming news aggregator with better categorization than HN and less noise/navigation effort than the myriad subreddits would be a great tool.
e. also Chrome PageSpeed says you should compress your assets, though that doesn't seem to have much to do with the speed issues, since the hangup is loading the article list, not the app itself.