I still have yet to drive, but i rode along with my girlfriend to go grocery shopping. At this point, i'm not confident that i could completely replace my vehicle. It would be "less-than-convenient" to have to go grocery shopping multiple times per week because i can't haul a full load on my bike.
I also play adult league baseball and there's no way i'd be willing to ride to all of the games. We play on fields as far as 20 miles away.
That's not really the point, though. I am fully confident that at the end of this challenge i will be more likely to ride my bike to places i normally would've drove. That will improvement enough for me.