It depends on what part of town you live in. Tucson has good telephone lines and bad ones . . . mostly bad!
I have been with TheRiver.com for over 4 years now . . . and they keep getting better. They use all fiberoptic lines at ther servers, and are linked with Covad for DSL, IDSL, and ISDN, and they are linked to iPass for global toll-free connections anywhere in the world.
Earthlink is OK here, but their speeds suck . . . v.90 gets about 33 Kbps on average.