I think there is a bit of a benefit to the LE/CE/SE coming out at the same time, that wasn't touched on. That benefit being the ability to save some money.
Say you are a fan of a new game coming out. You buy it on day one for $60, then 4 - 6 months later they release a "Special Edition" with some misc trinkets, soundtrack, etc thrown in, and they are charging $89 for it. Being a fanboy and wanting one, you may now be spending $149 for the game and the extras. Great for the developer, but bad for you. Granted you may be able to get some money back for a trade-in or selling the extra copy, but you still will pay more then just buying the edition you would have wanted. I see it as a benefit to the gamer.
From what I've seen, most people who buy the special edition know they like the series and so shelling out the extra $10 - $50 is not a big deal for something they enjoy and/or collect. For new IP's it can be risky though. As long as you are given the choice I don't see the problem. If we were all forced to buy the Legendary Edition of Halo 3, I would have my torch and pitchfork with you.
Now sometimes where people can get screwed are the "Limited Editions" For instance, if you weren't sure about Bioshock and just bought the game and afterwards was thinking "Wow, I want my own Big Daddy figurine" well have fun paying double the price on e-bay for it. Although that is the nice thing about "Limited" editions though, you get to pretend you are part of some gaming elite who has 1 of 100,000 of something.