The author of this hit the nail on the head with the suggestion that people should visit with other folks in the area who are online gamers. A spec sheet from an ISP is mostly a marketing piece that doesn't realistically tell you what you'll need to know such as often network "lags" pop up, how often the network goes down, etc. Find the ISP that gamers in your area prefer and you can't go wrong.
It is very important to pick the right ISP from day one because a lot of those will offer introductory deals that bind you to a long term contract. If you pick a rotten ISP, you might not be able to switch to a better one without having to pay a termination fee.