Theme Development – framework?

Hey all,

I have been looking at various Theme frameworks and could use some help coming to conclusions.

Previously my approach has been to find a similar theme to PSD file then reskin and modify.

After some researching Thematic seems to be pretty popular as a foundation for developing custom sites.
Has any one experience with this, is it recommended? Is any better then this one?

The other things that concern me with Thematic and similar is the amount of additions and modifications to the system. This seems to bring it’s own set of problems. So I start to wonder is it even worth it trying to learn a system on top of a system.

Typically I build css html from scratch, test as I go. I am finding working through 7 styles sheets and over orgazisation too cumbersome. Am up for learning it, if it’s worth it?

Thanks for the time