Tried on different browsers and this doesn't happen in them. You are using chrome as I was? It may be chrome doing some strange stuff for same requests.
Note that I do
http://localhost:3000
and
http://localhost:3000?diff=true
and I get both of them in 10 seconds instead of 10 and 20 for the same request.
I would still love from someone to explain this, but maybe thats another question.