I was reading through the thread, saw this, and felt I needed to respond.
I don't think your complaints are valid, because much like The Matrix, the first act of Inception is spent introducing the viewer the the mythology of dreams, while the second act involves them planning their inception job down to the last detail. Maybe you missed something along the way that left you confused during the ending, but I'm sure a second viewing could iron that out.
As for the ending, I think there's a lot of things Nolan wanted to accomplish with the ending, and setting up a sequel was absolutely NOT one of them. And your comparison to Friday the 13th is extremely misguided. In F13, we watch Jason get killed, yet he pops up at the end in a moment that makes the viewer go, "Oh, great, he survived." I don't really think that ending is as thought-provoking as Inception's was, since the ending to Inception leaves a few clear-cut possibilities. The ending wasn't the least bit cheap, and you sound like the dude from AICN that was *****ing about it. Some people, like yourself, need closure in a movie ending and that's fine, but Inception just isn't that film. I mean, the ending sort of fits with the theme of the entire film so I think it fits pretty damn well.