If you're working in distributed systems, fintech, mobile network optimization, broadcasting, the first thing you should do is switch off Nagle's algorithm. Animats should focus on Second Life and stop holding on to what's now a very bad default.
My other work back then, on fair queuing, followed the same line - keep things from getting really bad just because something was slightly overloaded.
When I was working on this, funding was from DARPA, Defense Communications Agency, and such. They wanted networks to keep working under bad conditions. Maximum price/performance was far less important. The price of getting the last 10% in performance is usually complexity and often fragility.
1. Just because you haven't "encountered a single environment" doesn't mean you haven't been in one or that you'd even know what to look for to know if you were in one where it would be a net win.
2. "If you're working in distributed systems," you likely have very fat, fast, and reliable pipes between your services. Nagle's algorithm is probably a Bad Thing[tm] in those situations. If you have a lot of Wi-Fi interference or dropped packets, Nagle's algorithm can be the difference between 50bps and 1mbps (assuming your application isn't filling packets), except that Delayed Acks prevents you from realizing all that.
There's no "one size fits all" solution, but you have control over Nagle's algorithm, you do not have control over Delayed Acks.