Pink Bike have just published a pretty in-depth review of the 741 wheelset. You can read the summary below and/or click here to read the full review.
"There's no doubt about it, the 741s have convinced us of the benefits of ultra-wide rims. They allow the tire to provide more traction, make for a more forgiving ride, and also proved to be a much more reliable setup when running low tire pressure. This last point was shown to be true when one large rider able to run at least 10 PSI less than his usual pressure, and the other more average sized tester preferring about 5 PSI less, both with out any burping. The 741 wheelset isn't exactly inexpensive, but at $1,299 USD it does cost less than many other carbon wheelsets on the market that feature standard width rims. For this reason, and because of the benefits talked about above, we'd be far more likely to purchase a set of 741s before any of those other options." Mike Levy
There's no doubt about it, the 741s have convinced us of the benefits of ultra-wide rims.