My XC race bike I have just spent £1000 making lighter! I was using 06 rebas and 2kg wheels, upgrading both of them should make a big difference.
my winter training bike is a 32lb trance x3 08' heavy, but for training and mucking about in winter, its all you need.
I would say yes, some people take weight saving far to seriously. But for others, they have to do it so that they arent racing people on bikes 10lbs lighter than theirs.