IMO the real advantage of STI is when you're on the hoods, climbing, out of the saddle, and you want to shift without sitting down. That kind of sustained climbing doesn't happen in a CX race.
I built up my cross bike with a bar-end shifter because each time I had crashed my singlespeed I knocked the levers around, and was glad there weren't shifters integrated with them. There was that "aha" moment and the way Surly builds up the cross-check made a lot of sense.
If you were used to STI, bar-ends might drive you a bit nuts, especially if you were still using STI during the week. My wife thinks I'm a bit silly for choosing bar-ends, but obviously there are many people out there who see advantages to them.