Anyone Upgraded from 2012 MBA to 2013 MBPr?

I currently have a 2012 Macbook Air base model (128GB SSD, 1.8GHz processor, 4GB ram). Has anyone upgraded from this model to one of the retina Macbook Pro models? I was considering selling my MBA to upgrade to the mid range 13" retina MBP (8GB ram, 256GB SSD). If you upgraded or use that model, did you notice a huge performance increase? I'm trying to decide if it might be worth going with the 15" Retina.

Thanks,

Well, I just pulled the trigger on the October 2013 15" Retina Macbook Pro. I'll post back with my thoughts when I receive it this week.