there's a UI system someone posted a while back that allows android to operate in a 3-viewport mode, where you have 1 big viewport, an 2 smaller viewports, each running a different app. and you can switch between them. there's also ixonos' thing...which is a windowed UI. i personally prefer the former, because it wastes less real-estate.
neither of them are available atm, but they will soon.
although i don't think you can run multiple instances of the same app.
oh yea, the adam ink has a multi-pane launcher as well, which works just like the first one i described, and that's already available...although it doesn't seem like it's very good.
either way though, android, and especially honeycomb is capable of multi-tasking, i think it's just a question of ui issues, and everyone is trying to find the best presentation for such a function.
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