I have a 1.2. I too got the itch to upgrade. I toyed with the idea of upgrading to 105's, wheels, etc.
In the end I realized that any money I spent upgrading the 1.2 would be better spent on buying a whole new bike.
At 21lbs there just simply isn't much room for weight savings without spending a LOT of money.

Got the Giant TCR Composite and couldn't be happier. I've since put Williams 38s on it and it's right at 18lbs.
The 1.2 is permanently attached to my Trainer now (unless the wife's bike is on it). There is nothing at all wrong with the 1.2, just not worth throwing much money at IMO.