I don't know about overrated. The average Joe is likely to find live chat to be of help, and the questions he has to ask are pretty simple. If live chat can give a good % of customers instant answers/solutions, it's still a very effective support method, that will be appreciated especially by those who can't afford long distance calls.
gives us some insights into the results of live chat. Sure, things can be better or worse with other companies, and we should not conclude that the live chat satisfaction levels represent the overall customer satisfaction with the company. The comes only after using the tickets system.
A company could of course employ Level 3 techs for live chat. That will reduce the number of "you'll have to submit a ticket" responses, but that's high end service costing top dollar. One gets what he pays for.