There isn't *that much* of a difference if I buy the latest Tim Schafer game from a major publisher and it turns out to stink, or if I fund Tim Schafer's Kickstarter campaign and get the game "for free" and the game turns out to stink. Really, there are 2 differences: (a) if the publisher makes the game first, I can read the review before I buy; and (b) in the kickstarter model, Tim Schafer probably has more creative control. Therefore, the whole thing comes down to the question, "Do I generally trust Tim Schafer to make a good game?"
Actually on Kickstarter you are buying *a promise* that some time in the future, if all goes well, you will get a game, a book, a dvd whatever. I wouldn't compare it with investing and the stock market either, because if a project goes really really well the "investors" won't see a dime extra than what they initially pledged for.
The complaints I've seen are usually about long delays, delivering less than promised, Kickstarter exclusives ending up in retail boxes and retail being much cheaper and not any slower than getting it from Kickstarter (especially if you are from outside the US). The only apparent advantage as you said is that you remove the middle-men but, unless projects start improving on the other aspects, people will become more hesitant to give money or will give money only to "sure bets". Of course "sure bets" had other ways of raising money so the "fad" or "bubble" of the new, unknown guy or gal crowdsourcing a new idea is going to deflate. In fact, it has already deflated a bit because a lot of the new projects are from established companies that use Kickstarter as a market survey tool and flexible pre-order system (see for example the ogre project by SJ Games).