I could give you some first hand advice. I had a 2011 Epic Expert 29er EVO R and really liked it. I was racing Cat 1 xc and thought the bike was perfectly suited for the purpose. The I decided to upgrade last year to a 2013 Epic Marathon. I did a lot of endurance racing including the Wildcat 100, a 12 hour solo race, and the Hampshire 100. I thought going back to the double was better gearing for longer events. I also noticed the functionality of the brain was improved. It seemed to have a better transition from locked to active. This year I plan on sticking to 50 milers, a 6 hour solo, and a 100k. I'll also sprinkle in some regular xc races. When the Epic WC came out I thought it would be the perfect bike, but wasn't sure about the geometry change and stiffer suspension tune. I really liked the idea with the 1x11 so I ended up buying one. After riding it for the first time today I'm glad I did! The bike feels super quick and responsive and the brain works seamlessly. I ran the front and the 3/4 closed and it felt like I was riding a fully rigid bike until I hit trail obstacles, the transition to open was even smoother and with no clunking sound. I rode more out of the saddle and the bike just wanted to attack everything. It was a noticeable difference from my 2013 and way better than the 2011. Is it worth it? The depends on your feelings, but I certainly don't have any regrets!