The previous server ran Apache, and I'm using asp.net 4.0. There's no doubt the the new server is more robust than the old one, but my previous experience was that even on the most robust servers, .NET just couldn't handle the strain of a high-traffic site.
Most of the pages on the site use typical controls, but here's the catch: using the typical controls on the high-traffic (main content) page resulted in load-testing showing the page could withstand 17 hits per second, which basically means the page would not be functional on this website.
Using the stringbuilder resulted in the page being able to withstand 300 hits per second, which is acceptable. You might say that I've coded this as a nube, but I coded it in a way that works, where otherwise it wouldn't.