I dont think Comcast's statement about using IE 6 or 7 is true in saying you will get the best of speeds.

I'm going to assume that if your system is something like mine where I have dsl it goes phone jack > DSL modem > wireless hub router > computer. The cable would not be much different most likely.

If you have your port settings on your router to be open to port 80 which is standard http, you will always get the highest speeds no matter what system you are using, or what browser. Your download speeds are rarely, and I do mean rarely affected by what browser you use. I have Opera, Firefox, and IE (its like IE 4 or 5). I have downloaded using them all and I've always topped out at about 92.5kb download which is the max that I can be at.

Microsoft is trying to create a monopoly is seems like, they always want you to use their software and no one elses. The make it seem like as if any other software or OS that is not from them is bad. There are always options and such for you not having to use their software. Only MS thing I use on my computer is the OS itself. Web browser, media player and so on are all from other companies or open source programs.