In particular, "It's just a bunch of things in Merb that we don't do. For instance, is like the classic one of Symbol#to_proc, which Rails does. Actually, Rails recently took out a bunch of use of it, because is 10 times slower on Ruby 1.86, so it's just the things that we don't do in Merb that give us a lot of performance right out the box."
and http://www.infoq.com/interviews/katz-merb
In particular, "It's just a bunch of things in Merb that we don't do. For instance, is like the classic one of Symbol#to_proc, which Rails does. Actually, Rails recently took out a bunch of use of it, because is 10 times slower on Ruby 1.86, so it's just the things that we don't do in Merb that give us a lot of performance right out the box."