Quick releases weight is going lower and lower every years. I've done a quick comparative to evaluate their quality compared to long and well proven ones.In this comparative, you'll find these QR: SHIMANO Dura-Ace 7800, CAMPAGNOLO Record, MAVIC (the one you have with Cosmos for example), BBB, TUNE AC14 and m²racer.
A difficulty to place the washer just in front of the cam before the tight operation(they both have to be in a position to be able to tight). A few seconds lost while putting this cam in the right position, then the tight is good, we feel well that the quick release is in place and is well tightened. The untight operation didn't cause any problem in spite of a weird metallic noise, it doesn't have to be too much tightened it seems. A races QR set because of its weight and its quality but it doesn't have to be put for a wheel change since the washer that has to be put against the cam is quite hard to put right in place and will make you waste precious seconds during a race.
EDIT: After having read again the user manual, it's mentionned that the cam and the washer have to be held in one hand while the other hand turn clockwise the end nut against the frame, it's then possible to tight thanks to the lever arm with no misalignement problem. A non common way of use for this astonishing product!
Really easy to place, there's no evident position from the closed and the opened position. But one can feel that the QR does its work. The lever arm has to be placed against the fork, otherwise it may enter in contact with the spokes in the case where it would be firmly pushed by accident. The untight operation is pretty easy even if the lever arm is placed against the fork or the frame. Quick releases that can be used for races without any problem.
SHIMANO Dura-Ace 7800:
It's very hard to turn clockwise the end nut on the thread, it makes lost some seconds because one have to force to screw it up before using the lever. This disadvantage is caused by brand new quick releases I think. With some wear, the screwing up operation will be easier. Opened and closed positions are evidents and the sturdy arm lever gives a huge strength to tight the wheel. High quality QR that need some running in or end nut preparation to make it spin easier on its axle. The set is heavier than the ones presented just over.
I didn't have them at home so I picked up a picture of them on JulMTB.free.fr. CAMPAGNOLO QR are all well finished but unfortunately I could never fell any big difference between the opened and the closed position. They're really good but still, they have the same problem as the Dura-Ace ones. The end nut is hard to turn on the axle's thread. These QR are almost indestructibles.
I didn't meet any problem, closed and opened positions are evidents, the utight is as easy. Definitely the easiest QR to use. On an other hand they are quite heavy.
A bulky lever arm makes the quick release look bad, the tightening force seem low but is certainly high enough. The lever reaches a maximal position when it enters in contact with its stop ("butée" on the picture). The weight is good for middle range quick releases.
If one had to find a winner through this mini comparative, it would place the TUNE ones in first position. Their weight is really low plus they are easy to use. It makes them inevitables on many bikes as Jan Ullrich one.
Mavic quick releases are good as well while the BBB would take the last place, I wans't really satisfied with them, even through I use them daily on my training wheels.
The m²racer are excellent and incredibly light (the lightest at the moment) but for aren't that good for wheels replacement during a race especially if the team mechanics doesn't know the product.
For the SHIMANO and the CAMPA, I'd say that it's almost impossible to wear them out until they're unusables!!