One of the big hassles with UCarShare has been the need to return the car to the same location, so I really can't make a one way trip with it, or even a trip with a long duration.
My habitual trip is out to karate, in either Park City or Sandy (both about 16 miles away). Neither location is well served by transit--Park City not at all, and Trax is about two miles away, downhill of the dojo. Karate lasts somewhere between an hour and an hour and a half, and the drive typically takes a half hour. Using UCarShare for the drive would require a rental of about 2.5 hours, and about 35 miles of travel. It's a trip I typically make 2-3 times per week. Net, that comes to about $12 for every training session, which is totally unsustainable.
One alternative is forty five minutes on Trax, fifteen minutes drive to the dojo, an hour of training, a fifteen minute drive back, and forty five minutes on tracks. So for every hour of training, I spend 2 hours traveling. Which costs about $7.50, plus $2.00 for Trax.
I'm fortunate to have several dojo mates who live within a mile, so car-pooling has often been an effective solution for Saturday trainings, but less so for evening trainings, as we all come from work, rather than from home.
The biggest impact of transit dependency is not the time spent traveling, but the trips that aren't made (or can't be made) because of timing.