Servers are where the problem is. The GIL makes python functionally single-threaded, which is a bummer for your server at any kind of scale. So you end up having to have n cores' worth of server processes behind a load balancer, even if you only need one server machine, which is a bummer if a you have a stateful server (such as a game server), as you now have to manage communicating state between processes by storing it in another process (frequently Redis).

But python is easy and fun to write code in, and "developer time is expensive, servers are cheap," so there are a lot of python servers which could benefit from a lack of GIL. Never mind that it's fast to write, but difficult to maintain since it is a dynamically typed language and one typo creates runtime errors that any statically typed language will catch at compile time. Or that it is slow. Or that a python process never really releases memory back to the system, just within itself, so the process slowly grows over the course of a few weeks. Or that the Twisted framework you're using for cooperative multitasking because of the GIL is really easy to block on a database query by accident, leading to uncooperative multitasking (= large lags), resulting to forced server restarts, and loss of players (= loss of revenue). So yeah, "developer time is cheap" but it's sort of an expensive cheap. I came to the conclusion that python is unsuitable for servers, but until Go came out, there wasn't a realistic alternative, since C++ and Java are too heavyweight, and Ruby suffers from similar problems (don't know about a GIL).