I've used all the recommended theme frameworks out there from Headway, Canvas (WooThemes), Gantry, StudioPress and so on. From my experience, PageLines Framework was the most enjoyable to work with.
After a few days working with PageLines, I quickly purchased the premium version and haven't looked back since. There custom service is unbelievable, the forum staff are really helpful, they don't just provide you with the answer to your question but also provide links to useful resources and alternative ideas.
If you're new to WordPress, I highly recommend you give PageLines a try.