[dredmorbius]

It really depends on the circumstances.

If you're 1) rushed (have places to be / people to see / work to do), 2) the weather's poor, 3) you're female (the area's improved but it's still not the best side of town), 4) you're risking a 60+ minute wait if you miss the train, etc., it's not particularly pleasant.

Walking a similar distance along a different or safer route, where I've got the time to wander, or where transit service is such that I've only a few minutes wait (or as is more likely the case on much of Muni in SF: you've simply no idea and the wait may be anywhere from 10 seconds to hours), the situation's not so bad.

But miss your CalTrain connection and you're 30-60 miles from home in a part of town with not much to offer. Though that too is getting somewhat better with the ballpark and revitalization going on.