The post Build WordPress Sites Fast With the Thematic Theme Framework by Es Developed is a great resource for anyone wanting to get started with the Thematic Theme. It lists over 40 resources and tutorials that’ll get you where you want to be with rapid WordPress Theme development.
And there’s some great explanation behind why you’d want to use the Thematic Theme. Under the heading Don’t Touch That Theme:
To create your theme, you don’t actually edit any of Thematic’s theme files. Instead, you make changes using a separate child theme.
It’s really powerful since you’re not actually touching any part of Thematic. You just get a nice starting place, without worries about future Thematic updates overwriting your code edits.
You don’t have to rewrite a bunch of code all over again–you’re just adding the bits that you want to be different. This works very much like the custom styles on WordPress.com hosted blogs.
Make sure you check out Build WordPress Sites Fast With the Thematic Theme Framework.