I used it for over an hour last night and saved .5 seconds. I wouldn't care if it saved me a whole 15 minutes (which it would have to be 1800X more efficient than it is now). Breaking sites and or speeding things up at the expense of other site owners isn't worth it to me. If you have slow broadband – there are other providers out there.
I have no qualms about blocking it and telling visitors why they were blocked. No different than presenting a user with an error "You must have cookies enabled to shop this site" for a cookie based shopping cart or login error to site that requires cookies.