Greyhound is NOT as bad as people are making it out to be. In fact, I was pleasantly surprised. I was half expecting to have the worst travel experience of my life, but it ended up being relatively pleasant and a heck of a life experience. I must say, my standards were substantially lowered because I read horror stories and bad reviews on yelp before my first ever greyhound trip. However, I spent nearly 40 hours roundtrip either on a bus or at a station on layover and I can say with all honesty that I'd do it again.

In regards to the sf station in particular, it is totally fine. I was completely shocked that people would call this area of San Francisco sketch. Union Square has more homeless and questionable individuals than the area around the newly renovated SF station. Seriously, this is SOMA and not the Tenderloin. I'm a college aged female and felt totally safe. I scoff at anyone who says that this station is sketch.

Pros:
Very cost effective
long rides will give you time to think, catch up on reading, ect
Scenery (depending on your route)
You'll probably get at least one good story out of it
The possibility of meeting interesting people

Cons:
Could not sleep a wink (although other people seemed to have a problem with it)
There is a potential for sitting next to people with babies, smelly people, ex-convicts ect. But I guess that is the risk you take whenever you go out in public.

I would reccomend this especially if you are a poor college student strapped for cash and looking for some good old life experience. Just be prepared for boredom, bring some food for long journeys, proceed with some common sense caution and you'll be fine.