I've ridden my Di2 bike less than 10x and I am sold - I've tried hilly, fast club rides and 1 race so far in it.

I'd like to get Cav's take on Di2 vs Red...but we'll never get that of course

The 10sp Ultegra version should go down in price soon. I got mine 1475 and was able to pick whatever config I wanted (the seller gave me a DA chain but since I've only used KMCs and 9sp Shimano before I don't know on how much difference does it really make).