In addition to page load issues, they also more or less completely solve the Slashdot effect (aka the Reddit Hug Of Death, these days). A competently-configured Nginx server on a 512mb VPS, serving static-only content, will handle ridiculous amounts of traffic without flinching.
Ever since a front-page mention on BoingBoing took down my feature film BloodSpell's site immediately after release in 2007, avoiding server load on a site has been high-priority for anything I'm launching that is likely to have bursty traffic.
It's nice to see usable tools for managing larger sites with a static generator developing and becoming popular.
I'm very much in the Nginx/static camp, but it would be useful to know how bad the spikes can get.
It was very interesting to see and was quite a lot of traffic for sure.
Bear in mind that the screenshot he posted is for concurrent visitors too.
Hopefully this doesn't reach that level of awkward and your info was really cool to see in that Reddit thread.
Reddit depends wildly on the size and activity of the subreddit you're featured on. Imgur shows view stats, so you can get some idea from that.
For scale on whether nginx can handle that sort of load, I've had tiny VPSes sitting there happily handling 200 SIMULTANEOUS users serving static files, which translates to between 500,000 and 3 million uniques a day, maybe more depending on your site design.