Wheelsets aside, it makes a noticeable difference but in my book it's hardly worth the expense/hassle. Even knocking off a pound or two makes my bikes feel a tad more zippy, accelerate nicely, pulse up grades, etc., etc. Lightweight saddles? - I do like them, the bike doesn't labor when you swing it side to side. But it's hardly worth spending the money when losing 5-10lbs off the body will get in a better overall result. I'd take a lighter body/heavier bike anyday.