I use Thesis theme in my personal and clients website. It's SEO friendly and easy to maintain. You may find it a bit expensive but it worth every penny.
I don't use it.... When there are lots of free ones available... But I admit that thesis has a great and simple design, fully seo optimized.
I am using thesis theme for my PR2 website. A very good option for seo and for design also. I think it is expensive but you will not loose your money and you will be rewarded a good traffic.
I don't think SEO options in Thesis theme persuade me to buy it. I bought that for the versatile wordpress customization options it offer. You can have the same SEO settings just using 1/2 plugins, you don't need to buy the theme for that.
I completely agree, A lot of our highest ranking sites don't even use Thesis, I prefer to use thesis as a versatile wordpress customization as well. Specially since they added the option to export/import all options in Thesis 1.7. Great for designing for clients.