I switched from Verizon to Earthlink for both phone and dsl, mainly because EL "promised" 8 MB service as opposed to VZ's 0.5--my line due to distance issues can barely get 2.5 (which is 5 times the speed for VZ).
No matter what carrier you switch to for non-cable service, the lines to your location are still VZ's. If a problem occurs you could be without service (as was my case) for weeks at a time, waiting for EL and VZ to synchronize their operations, and VZ is not going to be too quick for an EL customer. Consider this before switching.
PS: Ultimately VZ found there was a short in the line between me and the main box, an issue VZ is responsible for and not EL,