Maybe no users complain, but as a developer I often think, god damn, why is there so few RAM in there. And no iOS doesn't do memory managment seamlessy, the responsiveness comes from developers working hard to constantly cache/unchache everything that might take up a few megs.
I think they did everything to get the price down to $499 - including removing camera and reducing RAM. I'm guessing they thought that the $499 price point was required to make iPad a hit.
I doubt supply constraints are an issue. They're the single largest purchaser of flash memory in the world[1]. I imagine manufacturers would be bending over backwards for them, since their orders must all be quite large.
