If you seriously have an alternative to Comcast, TAKE IT!!!!!!
Comcast is "fast" sure. But they're also deceitful, lose packets like nobody's business, and are terrible for gaming. AH runs okay, but 90% of my online FPS gaming reeks because of hits not registering.
On top of that you may get "X" mbps speeds, but they actively clog their own bandwidth to keep folks from using more than "Comcast" wants them to. They actively send out signals that terminate many file-sharing files, legitimate or not (they don't want you using their bandwidth with the off chance you're pirating MP3s), and are currently being sued -- I think in a number of states -- for false advertising, bad business practices, and many other seedy underhanded doings.
Oh, and yes they're the company that gives you good service for 6 months then suddenly they flip the switch and you get crap the rest of your life. Many many reports of this kind of activity from Comcast.
For me it's the only option. It works but by god if I had reliable DSL at high speeds I'd probably use that.