I am very happy with my Comcast. I get 12 to 15 Mbps on my WIFI, more on the hardwire.
We also have digial voice and digital TV. All work great!
I heard a report a while back with evidence that Comcast detects for customers running those online speed tests. Comcast then prioritizes the network to make sure the packets for your test blast through. IOW they try to make it look like you get better bandwidth and latency than you actually have.