I live in California and have Comcast, and I unimpressed, but they have no competition, so they don't need to improve.
My max sustained download, now, is about 2.2-2.4MB(ytes) and and 240-250KB up. When I got the service 6 months ago it was closer to 2.6-2.8MB and 275KB up, but somewhere around beginning of summer, speeds dropped.
I've called them on the problem, but their response is 'well, we can ping you, so no problem'. Their way of measuring bandwidth problems is by having someone come out with a *signal strength* meter to check their signal -- if they find no problems, then they charge you a $100 house call.
The problem is worse during the day, with the worst time being from late afternoon till late evening -- typical of being on an oversubscribed cable loop. They *claim*, I'm not -- and that the business class lines are separate from residential, but I can't see them laying out separate loops for business and residential just to provide separation for 'business' customers who are in a residential area. Even if I could prove a problem, their 'minimum' guaranteed speed of 2.5Mb suddenly becomes "within 10-17%" (basically anything over 2Mb, and they won't consider it a problem).
Of course I'm welcome to find service if I don't like what they offer me.
DSL in my area gives sells a line rated at 3Mb(its)/768kb, which yields about 315-325KB down 62.5KB up.
To add insult to injury: If I use a speed test like DSL reports, because of Comcast's has tuned their burst cutoff to be just slightly above the speed-test's length, it will show 4MB down and 220KB up. The upload is slower than my normal measured, since it's right after the cutoff kicks in due to the download.
Comcast has yet to upgrade Santa Cruz to their 2nd generation. I believe 'etheric.net' has faster, but they are out of my price range, with 3Mb up&down @ $400/month (but no cap!...such a deal!) :'(