I run into this about a year ago, and have never looked back. Every new wordpress site I start now I run thesis and then just customise the theme that way. It is a bit harder to customise than your average wordpress theme, but with a few little plugins like Thesis Open Hook and then all of the Thesis in built options, it can be very easy to use, and you can be customising (the basic options) very quickly. Well worth it for the unlimited site licence version.