said by tshirt :

People who have had a poor experince with any service provider tend to be loudest, so negitive stories you have read may represent a fairly small minority, my feeling is the vast majority of cable users a fairly satisfied (sure, many WISH for cheaper/faster, but do fine with what they get)
because ComCast is made up from many different systems aquired or built over many years, actual experience varies greatly by area.
Ask neighbors, local friends, etc. about how your local system does, will tell you much more then generalized nationwide reports.
There is no contract, and often the modem and install (if needed) can be gotten free, so try it and if you don't like it, quit