Frameworks in WordPress for a Programmer

I’ve been developing websites for a few years, mainly using other CMS systems or php applications.

I have a few clients who I have made small (I mean really small) changes for on their wordpress sites. And since then have wanted to get deeper into WP theme development.

There are a lot of wordpress ‘frameworks’ (Genesis, Thesis …) but these seam to simply add an extra layer of unneeded complexity to the theme development. I expect their advantages lie in allowing designers to customise the layouts without having to without get into coding or template editing.

So my question, would these frameworks offer a real advantage (faster theme development times) to me (a php programmer) or am I better off developing for ‘pure’ wordpress.