I've never ridden a Campy bike...never even seen one up close. I'm trying to find out information on how exactly Campy (Chorus specifically) shifters work. I understand it is some sort of "thumb button" that is used to shift. My question is...is this thumb button used for both up & down shifting? And if so, can someone explain how? Or is the thumb button used for shifting in one direction, and then the shift lever moved (similar to how Shimano levers work) to shift in the other direction? Is the shifting with Campy Chorus smooth and effortless? I'm spec'ing out my new Seven Axiom SL and I'm trying to decide on components. Initially, I was deadset on Ultegra Di2...but after doing some research on the Seven Forum, I'm finding lots of owners are very happy with their Campy Chorus set-ups. The Campy would end up costing about $400 less than the Di2. Any thoughts from Campy riders out there? Thanks!

Linda