Last year I rode up to 200 miles / week in some serious mountains, did a few races, and trained with some hammerhead roadies all on Sora bike.

It was nearly flawless - and continues to be so even after 2 minor wipeouts. It has required minimal maintenance - literally one or two turns of the barrel adjuster every 6 months or so.

This was 2009 Sora. Yes, it's got a thumbshifter, but I actually really like it.

My other bike is Dura-Ace 2009. Guess what - it's better, but not by much. My Sora is a triple, which makes it inherently shift a bit slower, but I don't notice much difference in the RD shifting, which I find remarkable. Amazingly, I've not once had a ride where I thought "damn, I wish I had my DA here" since the Sora works so well that I barely even notice it.

I'd go 105-DA if you were going to be a serious crit rider, since that requires some very aggressive shift changes at high pressure, but for literally anything else, the current-gen Sora is excellent.