These small speed 'upgrades' from comcast are just the tip of the iceberg. With Verizon FIOS service that rolled out in my town this month, residents on comcast are saying bye bye.
It's a no brainer with more than 3 times the speed and at the same time $5 less per month ($39.95 for me w/ basic phone svc which I already had).
The Verizon service rep told me on the phone they are getting a huge demand. They will be expanding their service at faster rate and I bet they'll eat comcast's lunch unless the cable company gets more competitive.
Maybe there is some technological reason why they can't do it, but I think comcast is nuts to just offer me a speed 'bump' from 3mbs to 4mbs a month or so ago, since they were aware FIOS is coming to town. I was one of the first customers in town to sign up on cable internet and have stayed with them thru roadrunner, then attbi, now comcast. I'm still renting my orig motorola 3100 from them (I know, what a waste of money in rental fees). But that is money comcast is about to lose - many times over.
Once I make the switch to FIOS (Apr 6 install), I'm not going to the hassle of switching back (email address, etc) unless there is a very compelling reason.