I also have Comcast and I'm not getting quite the same results. . .

Although that could be for a number of reasons:
1) I'm using wireless B (I use my laptop almost exclusively, mainly because it's about as fast as my tower PC and I can sit on the couch, the porch, etc. with it.

Just tried it on a hard-wired PC and got this:

2) There's quite a few computers in my house sharing the connection, someone is probably doing Windows updates or using LimeWire or something.

3) We've got two Vonage lines (one that my dad's work pays for, mainly used as his fax line, and one for the house phone). That's probably the big killer.