I guess it's cool. I probably wouldn't use it. I made one - http://rollyo.com/rjhinson/shopping/ - it's the sites I usually go to when I'm online window shopping (haha), and it was kind of neat to be able to search them all at once for a particular thing, I admit, but that's not typically how I use those sites.
I'm sure it would be cooler if I thought of a better set of sites to use it for. I'm kind of interneted-out at this point. Too much... must get away. Need vacation... ::zombie face::