Interesting that this thread got bumped back up:
After I first posted in 2009, and bought the 2010 Force group, I used it and was happy for 2 years. Last summer the right shift paddle broke off in my hand during a ride, so I had to "hobble" back home in my smallest cog. I had been in a couple crashes over the two years, so I can't lay blame on the lever, but it was still a disappointment.
So I decided to replace the levers with the 2013 RED levers and also replaced the front derailleur so I could get the "Yaw" action feature. It all works fine, and maybe the RED levers are a bit smoother, but it is not very noticeable. Of course I don't have them side-by-side for comparison, but I hardly noticed any difference in travel, effort, smoothness, clicks, etc.
Now I see that the 2013 FORCE shifters have been upgraded to near the RED, so they are probably really about equal. I can't really be sure if RED will last longer than my original FORCE levers. Too many variables.
I am still using 2010 FORCE cranks with the 2013 RED Yaw front derailleur, and that works perfectly fine.
For information: After I got the 2013 RED shifters, I was using them with the 2010 FORCE front derailleur for a while before I got the YAW derailleur, and that also worked just fine. They all seem completely cross-compatible. And I like to cross-chain mercilessly, both big-small and small-big, so if there were any problems I am pretty confident I would have found them.