(Technically you can change them, but what I'm describing is the experience that 95% of the users will now have with the site.)
On Reddit you get an open source system with a one-stop appliance for any would-be submitters. The comment sorting algorithm is explained in a blog post by the xkcd guy (http://blog.reddit.com/2009/10/reddits-new-comment-sorting-s...).
On the flip side, reddit may not be profitable.
Considering they just had to beg for donations...
Speaking as one, I noticed the slowness and time-out problems basically went away as soon as they spun up those servers.
Whatever the financial relationship with Conde Nast, Reddit Gold is definitely a success.
Now user submits are really hard to hit the front page since their idea of a change algorithm is allowing auto submissions to hit front page with less than 30 diggs while user submits need over 100.