Dave Burstein here, not anonymous coward.
Lots wrong with Comcast, but their Internet service will generally be as fast as any of the telcos except Verizon. Most of the U.S. has a slow future.
Comcast's DOCSIS 3.0 in 2008 probably will offer 20-50 megabits downstream and no improvement on the upstream. It's a 120 or 160 megabit shared downstream. This is already deploying heavily in Japan, J:COM, some in Canada (Videotron), UK, France, and Holland. The only chips shipping (TI) are limited to 120 or 160 shared downstream and do nothing for the upstream. Comcast CEO Brian Roberts announced they will offer it to 4 or 5M of their 22M homes. The assumption is Comcast will use it defensively against FIOS and take a long time (years) to bring it to the rest of the country. Other U.S. cablecos seem even further behind.
The full 3.0 is not available for a while (more likely 2009 than 2008 for any volume). Full 3.0 is a minimum of 160 (shared) downstream and 120 (shared) upstream. Given typical usage patterns, most customers will get 20-50 megabits most of the time. The specification goes up to a shared gigabit, but I don't believe anyone is close to offering that as a product.
FIOS (or DSL) does not share the local loop, so there's no bottleneck between your home and the ONU (DSLAM) control box. Behind the ONU is shared fiber to the local office and from there to the Internet peering point. It is absolutely possible for that shared connection to become congested, and it was a common problem in poorly designed DSL networks. FIOS backhaul has been built pretty robustly, so as far as I can tell they have close to zero congestion problems, and customers almost always get their promised speed if the other side of the Internet connection can keep up.
Unfortunately, FIOS is currently only available to about 8 million homes, and Verizon has indicated they will top out at 20M or so in 5 years. The remaining 85M U.S. homes will have a second rate Internet unless and until the high end of DOCSIS 3.0 rolls out widely. (?2012-2015). AT&T and Qwest are planning for 1 meg up and 20 or so down, with most of the downstream used for their IPTV. They call it "Fiber to the node" but it's really DSL with a press release.
Conclusion: 60-80% of the U.S, will have a second rate Internet for years. I'd love for an uprising that tells Kevin Martin, Arnold Schwarzenegger, Randall Stephenson and the pthers powers that be the U.S. Internet should match world standards. Houston and San Diego should not have slower connections than Paris, Berlin, Geneva, Amsterdam, Tokyo, Boston and New York.
Dave Burstein Editor DSL Prime.