I'm gonna hafta disagree with the smurf here...rotating weight makes a huge difference. Upgrading your wheelset is one of the best upgrades one can make to a bike. If I had to choose between $400 worth of carbon chi-chis or a new, lighter wheelset, the hoops would win every time.

Fultzie, help us help you...do you have rim brakes or disc?
Are you a lightweight? If you don't weigh much you can (sometimes) get away with "stupid-light" for racing.
Also, if like many women you are more of a "finesse" rider than a basher, you can ride a lighter wheel. If, on the other hand you crash a lot and tend to throw wheels out of true, you might look for something a bit more sturdy...

That being said:
I'm old-school (and poor!)and have basic avid rim brakes.

My wheels of choice have always been hand-built; XTR hubs laced to some lightish Mavic rim (517s right now). I've also enjoyed the Chris King hubs (also laced to 517s) that I raced or awhile. They were tubless (Stans) and for longer endurance events it was nice to be able to run the lower tire pressure.