It's not the swapping, it's the (configuration) complexity and test performance, among other issues. See http://www.confreaks.com/videos/759-rubymidwest2011-keynote-....

I particularly like the example he gives near the end of always thinking they need to add the database and finally, after shipping to a bunch of customers, figuring out that they didn't actually need it.

In terms of test performance, I frequently see blog posts about reducing the time for a couple of hundred tests from half an hour to 15 minutes.

    marcel@localhost[~]time testlogger -a MPWFoundation ObjectiveSmalltalk ObjectiveXML EGOS EGOS_Cocoa MPWSideWeb
    tests:1: warning:  1055 tests (of 1055) executed, 0 failures (100 % success rate)

    real 0m2.939s
    user 0m1.607s
    sys  0m0.438s