I have the new 7800 wheelset, Shimano says this wheelset will only work with the new 10 spd cassette's has anyone run these or tried with 9 spd? I will eventually get the complete Dura Ace setup, but wondered if I could run the wheels until then?

I don't have the wheels, but one new feature of 10spd DA is that the cassette splines are deeper to avoid some problems that were common to 9 speed. This means that the 10 speed cassette will fit on a 9-speed compatible wheel, but the 9 speed cassettes will not fit on the 10 speed cassette body.

Looks like you're stuck with 10 speed if you really want to use those wheels, unless someone out there is making a 10-speed compatible 9-speed cluster (highly improbable)

I don't have the wheels, but one new feature of 10spd DA is that the cassette splines are deeper to avoid some problems that were common to 9 speed. This means that the 10 speed cassette will fit on a 9-speed compatible wheel, but the 9 speed cassettes will not fit on the 10 speed cassette body.

Looks like you're stuck with 10 speed if you really want to use those wheels, unless someone out there is making a 10-speed compatible 9-speed cluster (highly improbable)

Thanks, I'll just have to wait til I get the complete 10 spd set up!