I can't comment directly on the Cannondale bike. But, I can tell you that after riding Ultegra Di2 on my road bike all last season and then on my "A" CX bike in the fall... I'd be hard pressed to ride anything else (except the new 9070 di2!).
I think I appreciated the Di2 on the cx bike even more than the road. It ALWAYS shifted for me... no matter mud, water, etc. Also, not having to replace a single shift cable or mess with the shifting for the whole season is really worth something to me.
Now, it's back on my road bike and I sadly have to toss some regular 7900 onto the CX bike until late August. (or maybe pick up some new kit