Yes, Red is where it's at when it comes to the shifters. Everything else can be substituted with Rival/Force, which are still very light compared to Shimano components, but Red shifters are a must if you are running SRAM. My last bike had a full Rival group, and my new bike has full Red. The shifters are the only place (other than weight) where Red provides any noticeable difference in performance. That difference, however, is totally worth the money. I used to want Di2, but honestly Red shifting is so damn fast and trouble free that I really don't want Di2 anymore. The zero loss on the right shifter allows for rear shifting that's just as fast as Di2.

Di2 obviously offers the best shifting out of any component group out there, but Red is still so close that it makes justifying the price of Di2 very difficult. Ultegra 6700 and DA 7900 suck IMO. The only thing I like about 7900 is the no trim feature. Heck, I'd take Rival over 7900 any day.