Before they acquired AT&T, the service was quite poor. After the acquisition, it is a lot better. At work, there are certain buildings where nobody gets reception, and neither did I before. But after they merged with AT&T, I am getting full reception in these places whereas my friends with other service providers get no signal at all. (However countrywide, verizon is reputed to have the best coverage, if you travel a lot, you might want to consider that. I strongly recomment you NOT take T-Mobile. They currently seem to offer the best plans with most daytime minutes etc, but their signal strength is so poor in many places)
What are your experiences with Cingular in the Bay Area? I've heard that they don't provide reliable serivce, but has it changed due to their recent acquisition of AT&T's wireless division? Which cellular carrier should I go with if not Cingular? I'm most concerned with reliability....