My Felt has black Mavik Ksyrium Elites. I put 25 tires on them. It originally came with silver Elites, but I wanted to switch them for the black. My husbands bike had the stock wheels, which I thought were nice, but he loved the way mine looked and wanted them. My biking brother said my wheels were good and his were 'fine'. When my black ones arrived, as a surprise I traded my husbands stock wheels for my silver Ksyrium Elites and saved a ton doing that. His bike is about 3/4 of a pound lighter than it was, big whoop, but he loves the way they look and says it rides nicer than it did. I can't see how the wheels made that much difference and it may all be in his head, but he says so. Since mine have only had the Elites on them, I can't say if they made a difference on the two long rides we have taken so far, but I do know we rode further with much more ease than we did on the hybrids! Plus, I think they look cool.
http://www.mavic.com/en/product/whee.../Ksyrium-Elite
You can get the Ksyrium Equipe's for less money.
If you are buying them for a new bike you save a lot upgrading before you take the new bike home. Do I think they are that important or that much better than stock wheels? I don't know. It is a bit of hype, me thinks. But, maybe I am wrong.