[parasubvert]

The thing is, the multitasking tray displays applications in MRU order, so it already does what you're asking for in your last sentence. The tray as the equivalent to alt-TAB on a desktop, which is handy for MRU switching, but pretty annoying if you have lots of windows open.

I would presume most users, if they haven't used an app recently, or if they don't feel like using the tray, will just access it as normal through the regular menus or Spotlight search.

[solipsist]

MRU order works fairly well, although it's definitely not ideal. With the iPhone I feel that it lacks even more than it does with the computer. That's because of the fewer apps you can see on the screen at a given time when you're using fast app-switching. And since we usually have more apps open on our iPhones than our computers (because one has a "Quit" feature while the other doesn't), it becomes increasingly frustrating. MRU works great until your workflow starts to become more complicated and when the number of apps in the tray start to build up.