Originally Posted by
samkl
What's the benefit over a triple? Certainly doesn't seem cheaper. Even if you're concerned about weight (and I don't see why you would be on a touring bike), I can't imagine this weighs much less, what with the huge cogs and assorted extra parts.
Makes sense if your bike came with a 2x STI shifter, but otherwise I don't get it!
Well if we take the case of a stock bike then I'd argue that it would be cheaper (in general 2 chain rings should cost less than 3), lighter, but the biggest benefit is simplicity. I haven't had any real trouble myself with triples but it is more complex. Of course the 2x is only simpler if you don't have to use the Jtek adapter. Hopefully there are or will be road compatible front derailleurs for sub compact cranks.
I'd also flip your question around and ask what the benefit of a triple is. If someone gave me a custom one for free what would I get? With an 11 speed rear and 28-38 in front I think I've got it covered. I don't want a higher gear. Would I really want a 28-33-38? A triple isn't compelling for me.
Final point is that we may not have much choice. Mountain bike and road world are going to wide range rear clusters, compact or single front chain ring. I think touring cyclist are the only market still using triples and unfortunately we don't have much pull in the market.
I've enjoyed the comments by all. Some interesting observations.