As Matt says, bus systems are made bearable if you increase the frequency. A lot. Though you can also reduce the uncertainty-related negativity by providing more information. GPS linked signs telling you when the next bus will arrive. Alternatively, though less user-friendly and less worse for low income riders, one can have some sort of text message system you can access with your cell phone.
Obviously not all bus lines can have an awesome level of service, but if I were the benevolent dictator of the local transit system, I'd create and highlight a system of backbone bus lines, ones which had sub-every 8 minute or better service throughout much of the day. High frequency lines already exist, of course, but I'd promote them to make it more clear to people.
