Update: I can repro the issue pretty consistently if I have two browser windows open and I F5/refresh both quickly (flipping between the two).
Why would Sitefinity take 10 seconds to serve a page simply because two requests for the page came at nearly the same time? The normal load times for this page are .6-.9 seconds. This problem is independent from browser version, OS, etc. It's a server-side issue. I have turned on HttpWatch and other tools and client side is just waiting for the server to serve the page.
What sort of logging or metrics can I turn on to tell what Sitefinity is doing for 10 seconds while the clients wait? I really need more info about the internals of Sitefinity so that I can troubleshoot.