I'd rather have two $2k bikes than one $4k bike. I'm picking up a Cervelo S1 with Ultegra tomorrow. I will probably rebuild my Allez with 105 as a back up. I just like the idea of choosing what I want to ride on any given day. But then I dont race so a really super high end bike isnt that important to me.

That being said, I would imagine that 105 group will find its way onto a carbon frame at some point next year. Or sooner if the cops should happen to find my stolen Tarmac (which explains why I like the idea of having a back up!)

and I have a MTB beater/rain bike and tandem for other types of riding