"it is indeed paved for the entire length. You can ride from just south of Aurora up into Wisconsin. "
Now wait a minute. I've gone as far as just north of McHenry, and all of a sudden the paving stops, and it's old RR bed with the mega-gravel. NOT very road bike friendly. I haven't ridden that far since last year, so unless its been paved since then... I think at that point you're about 10 miles from WI border.
It's a little tricky getting through Crystal Lake. That's probably the worst marked section. And actually when you hit the county line, the name changes to the McHenry County trail.