"If you rewrite your program in a language which is 20 times faster, now you can support 60 users instead of just 3, which is great, but how then do you scale beyond 60 users?"
We're talking about 60 concurrent users. If I could do 60 requests per second I'd be a happy man. 60 requests per second is 216k requests/hr. Assuming 30 page views per happy readwarp user, that's 7200 uniques per hour. Let's say daily uniques at that point is 6 times that, 40k uniques per day. With 40k uniques a day I'd be a happy man. More importantly, 40k uniques will take me n years to get to. So you see, I don't need to "scale beyond 60 users".
Right now readwarp isn't even at 3 requests per second because requests can take several seconds with contention. But that's not ideal either. And it's largely because of the language and the platform.