I don't consider a few hours per month administering servers to be much more than the time I would spend working around Heroku's proprietary app model for the more esoteric things I would want to do. I would guess it's less, but I don't really know. Throw saving thousands a month into the mix and it's not something I'd lose sleep over. Database servers that can handle 10's of thousands of iops and web servers that can handle thousands of uncached requests per second makes machine administration a lot more pleasant than it was just 5 years ago. Hardware has been scaling vertically quickly enough that it's no longer strictly necessary to scale horizontally in a massive way as you grow.