SoMa didn't have the ball park yet so it was kinda sketchy anywhere past the highway, and there were a bunch of weird muggings/knifings when a person of the wrong race would go to the wrong bar or place. We knew not to go the Korean club on Harrison. Meth heads would surround the happy donut and south park was a bit of a homeless tent city, and while there were some of the same hotels near the convention center, the west hall hadn't been built yet and it was all kinda run down the way most of moscone is.
I used to do a fair amount of work in the Potrero hill area in 2000 or so and dreaded parking there. Then the bust happened and not only did a lot more parking appear, but many of the good restaurants in that area shuttered almost overnight.
We lived in lower Haight until 1999, and it was okay, if you could roll with a little bit of homeless person screaming in the middle of the night just outside the place we rented. Our cars were broken into a few times and we got a few parking tickets a year but that was the price one paid to live in SF. It largely wasn't worth it. First me, then my soon to be wife got a job in the south bay, we moved to los altos to skip the commute.
The funny thing is the big 'displacement' story in the city around 2000 was the gentrification of the Castro, where older more established gay folks were making it difficult for younger, poorer gay people to find places to live near the Castro (which is sort of the traditional gay nexus in SF)
IMO SF is in much better shape nowadays, and it has a lot to do with the thousands of tech companies in and out of the city employing people who add their money and the rest to the city.