Just curious... how exactly is Mission Control a "downgraded" version of Spaces and Expose? When it has been streamlined and combined (not two separate key strokes as in Snow Leopard) and with multiple monitors, your desktops are easily rearranged and applications remember by default which space they were in (which is not true for SL)...
Even though what you said may be true, it still comes down to preferences and a lack of choices.
1. In SL, I can access either Spaces or Expose. I'm not forced to do both like in Lion. Thus, on this point alone, to me it's a downgrade, since I have less choices.
2. On rearranging of Desktops(Spaces), though technically you can't move the Spaces, you can move all apps in a Space to another Space giving a similar effect. You just have to grab a part of the Space where there isn't a window open and you can drag all apps from one Space to another. Also note I prefer the fixed grid of SL's Spaces since I don't have to hunt to see where a Space might have moved to because another Space was created by say an app going Full-Screen. For Example, I always know that iTunes, if open, would be in my top-right Space, #3 out of 9. Therefore, I can move to it quickly with 2 clicks on my mouse and barely looking at the Spaces. Note the 2 clicks are activating Spaces which is a button on my mouse, and then selecting the Spaces. I don't have to activate Expose.
3. While mentioning rearranging, note that in SL I can easily move any app from any Space to any other Space, while it's my understanding that in Lion you can only move apps involving the current Space. This would be another reason I think of it as a downgrade since in SL I can activate Spaces once and rearrange the apps as much as I want without leaving the Spaces screen. In Lion, you might have to keep changing the current Desktop to rearrange apps on other desktops.
4. As for apps remembering what Desktop(Space) they where in
by default this is definitely a preference. I prefer the default is to open in the current Space, and then I just set which ones I want to always open in a specific Space and which ones I want in All Spaces. So though you can do what you described in SL, your right in that it's not the default.
Overall, I see Mission Control as a mix of too many things, and it also lost some of the abilities which I use in SL.
Again, I don't want to see Mission Control removed. I just want the abilities of SL that are lost in Lion to be returned.
