In the case of my commute I was wigwamed through lots of residential streets to get to the Illinois Prairie Path. This section of path is too rough for a skinny tire road bike, with at least one section that most folks on a mountain bike would even walk. One section is now marked as closed until May. (I don't know if a cyclists could still get through.)

Worst of all it has me west bound on the 4 lane road my work place is on, requiring me to make a left turn from a 50+ mph through lane into our driveway. (no dedicated left turn lane, and no shoulder to wait on) Plenty of our employees have been rear ended here in cars while waiting for a break in oncoming traffic. Knowing this, I always plan my route to come in from the other direction, so I only have to make a right to get into the driveway.

Overall mileage is about the same as my favorite routes.

Still, kinda cool and worth a look. I don't use any other mapping tools so I have nothing to compare it to.