I have a 6800 wheelset. Good and bad things about it.
I like the new hubs. Adjustment of the cones is a little tricky, but once dialed in they're good.
The 6800 has a no spoke hole design so that they can be run with tubes or tubeless without tape.
But, I did find they were tight when using tubes. I had to put a tube in one because of a hole mid-ride, and I could barely get the tube in. But, perhaps that is the way the tubeless goes.