I live in the center city (pop. 150,000) of a metropolitan area of maybe 250,000-ish people. The local bus system is supposed to be pretty good for an area this size.
The bus system works pretty well for me. I work downtown and live about 3.5 miles away by the shortest route. I happen to be near two routes, including one about a block away that runs once per hour. The other one is a little further away and runs about 4 times per hour during the business day, dropping to about 3 times later in the evening. This is one of the core routes through the city, so 4/hour is about as good as it gets in this system. They don't always run at even intervals, and one of times per hour is an "express" route variation that doesn't use the exact same route or stop at all of the same stops. Therefore, you need to know the schedule or you can end up waiting quite a while. You can also see the express bus go right by you if you're at the wrong sort of stop for it. The routes I use usually run reasonably on time. Both these routes run right downtown, so I don't need to transfer.
These bus routes used run more often, but they dropped some buses several years ago due to rising fuel prices and falling support from the government. That must have been a major disappointment for those who are dependent on the buses (I use them but have other options as well - mostly I bike). I think probably the transfer situation got worse at that time. If buses on a route don't run as often, it can become a major problem if the bus you're on runs behind schedule and you miss your transfer. Then the total trip can easily get excessively long if you have to wait 30 minutes for the next one.