These are my first full carbon clinchers. I've ridden Mavic's aluminum, non-aero Ksyrium series for 10 years, so my perspective naturally has these as a baseline. My rides with the ENVEs to this point have been in hilly areas with lots of 10+% grade and with one ride having 20 mph crosswinds. Nothing in the rain yet but, besides rain, I've ridden these wheels in all the situations where any weaknesses should show. So, what are my thoughts?
First, the wheels are very quiet. The DT Swiss 240 freehub is extremely quiet -- so quiet that one rider riding beside me commented that he couldn't hear the ratchet at all. The quietness means you get almost no vibration from the freehub, which contributes to . . .
Second, the wheels roll very smooth. Even at 90psi/100psi front/rear, the wheels seem to smooth out chipseal even riding winter training tires (Gatorskins). (I normally run 80psi front and rear.) I expected harshness, but these wheels are not harsh by any means and they roll smoother than my Ksyrium Pros on the same roads and even a little higher pressures.
Third, the braking. You get used to the jet engine sound on one ride. It's not loud. It's just different. (And it offers the added benefit of telling you when a brake is rubbing.) How good is the braking? It's not as good as with the aluminum Ksyriums but it's not bad. Certainly adequate. It's consistent. I never worried about lockup. (I have yet to ride these in the rain.)
Fourth, how about crosswinds? I rode these wheels on an extremely windy day with unpredictable crosswind gusts. I could feel the crosswinds push, but it was never uncontrollable or nervous. Not much more than it would have been with the low profile Ksyriums. I was pleasantly surprised. I wouldn't shy away from these wheels for fear of crosswinds. It's not an issue.
Fifth, how stiff are the wheels? Hmmmmm. Historically, I have adjusted my brakes to ride about 1mm from the rim. With these wheels, that was too close. On level ground, I flexed the rear wheel enough to cause brake rub at two points in the pedal stroke. I couldn't do it one-leg pedaling, but casual two-leg pedaling flexed the rear wheel 1mm. I adjusted the brakes to sit about 4 or 5mm from the rim. Problem solved. Pretty much. After the adjustment, I intentionally put a lot of power down, standing, on a steep climb. I wanted to see if I could flex the rear wheel. I weigh 174 lbs. and I was intentionally trying to flex the wheel. I did. Even at 4 or 5mm clearance, I could cause the brakes to rub going up that climb. Is that too much? You have to decide that for yourself. For me, it's not a big deal. I'm not a climber and I usually ride more steadily up climbs. This wasn't my normal climbing style. (But aren't dedicated climbing wheels pretty flexy anyway?)
But what about aero? This is the question everyone wants to know the answer to: Are they faster? The only answer I can give you is, "maybe." One a long, flat road where I normally ride at about zone 3.9 to 4.5 power at a given speed, I rode these wheels at low- to mid-zone 3 at the same speed. Was that due to differences in wind direction/speed that I didn't notice? Maybe. Was it due to differences in tire inflation pressure? Maybe. I don't know. These wheels seemed a little faster there. But at certain yaw angles, these wheels are measurably, noticeably faster than my Ksyriums. I don't know how often you can count on getting those beneficial yaw angles but, at those angles, these wheels are amazing. Startlingly fast. But straight into a 20 mph headwind? Not so much. I'm not sure there's much benefit straight into a headwind.
Bottom line: I'm glad I bought them. Great wheel.