These are very nice wheels indeed. If you have a bit of cash to spare they might not initially catch the eye, as they aren't deep section and aren't carbon fibre. However, they have a superb reputation for their enduring strength despite being under 1500g for a pair.
Here are their specs, as featured at mavic.com (Ksyrium, SL: Race and time proven technologies):
January 2012 I bought a pair of these wheels, new, from Pedal Revolutions in Norwich. They've said that the wheels will be fine for cyclocross and tandem, as well as the more conventional crit racing and commuting work. Let's see how they hold up!