You don't say what pieces are what, but if you have Sora shifters now, the biggest difference is with them. The brake lever does the downshifts and there is a second inner lever for the upshifts, instead of the 2nd button on the Sora. It allows upshifting in the drops. This shifting action carries all the way up to Dura-Ace. The hoods are shaped a little different a well, a bit wider and longer. It may take some getting used to.

I wouldn't be shy about upgrading to one version older technology, either. I'm in the process of upgrading from 5600 105 to 7800 DA on the Felt.