I wish I could bike more, but there are several considerations that make it far from a good solution for me.
I live about 15 miles (via an interstate) each way from work. Since biking on said interstate is suicidal and illegal, I'd be looking at closer to 20 miles taking local routes instead. That's each way. 40 miles a day seems a bit excessive to me for a biking commute, not to mention the time it takes to get to/from work goes from 40 minutes to 2-3 hours.
I would bike locally to errands within a reasonable distance (grocery store, and such). But often when I get groceries, I find myself picking up perishable items. And a 45m bike ride in 90F weather would undoubtedly render anything perishable unsafe. I also tend to buy a lot of groceries at once, and carrying that much crap on a bike would be bad for my already iffy back. One of those adult-sized tricycles with a large basket in the rear (with a cooler) would solve both of those problems, but those are bulky and impossible to store in an apartment, unlike a standard bike.