My most cpu intensive task is running the full test suite of a customer's Rails app. I can probably shave off a large percentage of its running time, but it also contains integration tests run with chrome. What I do to shorten the test time is running only the ones of the files that changed. The boot time of Rails is there anyway.

The CI system is still slower that my laptop. We are not really concerned about it.

I'm waiting for something to fail because $3000 on a laptop won't make me gain $3000 from my customer.