Chrome: https://chrome.google.com/webstore/detail/old-reddit-redirec...
Firefox: https://addons.mozilla.org/en-GB/firefox/addon/old-reddit-re...
It sucks because I love reddit, but it will be EOL for the people who made it what it is in about 3-5 years
I think they are well aware that a lot of older users (some likely heavy _content_contributors_) will simple walk away if they do this.
You can't sell ads if you don't have original content that drives traffic to your pages.... old.reddit.com as well as '.compact' are the price to pay to prevent a digg type exodus.
One of the more insulting parts of their UX.
I bet forcefully unsetting it bumps their usage metrics for the new site though.