After a few rides on various SRAM equipped bikes, I've made the jump. I was initially looking at Rival, but Brian @ Wise Cycle Buys made me what seemed like a good deal on the Force group. The cost difference wasn't huge over Rival groups I was seeing advertised. The carbon crank alone seemed worth the difference. I've actually noticed that many bikes that come with OE Rival group are actually equipped with the Force crank, though I'm not sure how much to read into that.
Everything arrived today, and I've spent the last few days assembling the tools,grease, etc... necessary to do the wrenching myself. I removed my current 5600 105 group from my Tarmac earlier this week, and the frame has been cleaned. I also had a local LBS chase and face the frame's BB shell for me. If all goes well I should be riding SRAM (on my trainer) in the next few days. I've done some minor tuning in the past, but this will be my first venture into complete buildup territory.
Between this and some Neuvation M28x Aeros that are on their way, my bike should be a totally new ride. Not to mention shed a decent amount of weight over the stock config.
Now I just need Spring to arrive in a big way.