My old Seven had a 9-spd 105 on the back and an Ultegra triple and front d. I switched out the 105 to an Ultegra - mainly to keep the components the same (and like Lisa, because I could). I can't honestly say I noted a difference in rear shifting quality. It tended to skip/hesitate in mid cluster if I were in an extreme (granny or outter) chain-ring...which my mechanic, after a throrough examination, attributed to "user error". A technique thing.
I then re-built the bike with a 10-speed, going to DuraAce with an FSA SLK compact crankset. That crank had a tendency to throw the chain off the outter ring. I put an anti-chain suck thing on the downtube to keep the chain from dropping inside. My new Seven has the same set up, but I put an Ultegra SL compact crankset on it. Full DuraAce (I think the cassette and chain are not, however). That think shifts awesome. I love that new crankset. And I love the black ice finish on it.