I bought the wheels for the simple reason that I wanted them. I did not expect them to make me faster, etc. Having said that, they do seem to be faster than my older (non-aero) wheels. It's hard to quantify, but the PR's are coming steadily on routes I've ridden for multiple years and many times.
I had no experience with carbon or aero wheels, and these wheels do feel different. The ride is slightly more harsh due to the deep section, but not overly so. I've read that people feel the 6.7s are easier to maintain speed with. That's subjective at this point but I would have to agree.
I haven't noticed any issues climbing, but even at 1500 plus grams these wheels are lighter than what I'm used to by 200-300 grams so that's not surprising.
Very happy with the purchase!
**I have the wheels built with Chris King R45 hubs.