Do it right and do it right the first time.
I made this mistakes pre 1.06, in anticipation that increasing MP level increase your rewards as Blizz put it, cough, cough... Guess what? no one farms in mp 10, to put it quite frankly, you got to be a noob to be farming in MP 10... This is more for an e-peen status and yes, i can run MP10 with my other gears in my stash but why would i? since MP0-1 is the most efficient... Why upgrade your gears now when its going to be worthless in a couple of months times...
I don't know if this is for e-peen, since I'm not doing this for ego. Part of what I enjoy about Diablo is that the challenges that each level gives you, and being able to pwn MP10 would be one of my goals in this game. I'm not sure if I would enjoy the game if all I do is grind lower levels for gold and loot. In that way, I have much better things to do with my time. I think this is all how each player values different aspects, and what they have created with D3 and the different MP levels is that they have changed the way that we play the game, even though the core of the game hasn't changed since it first dropped.
For me, I think being able to run MP10 for the challenge would be nice, and this opens the door for flexibility to choosing the "kind" of pace and game you want to play - from MP0 through MP10 and gearing according to what you want to accomplish (loot farming vs. XP farming, vs. key farms vs. playing higher levels for the challenge). It can create different games within a game. Speaking of which, I think it'd be interesting if we could find a way to do some kind of an D3-amazing-race kinda thing, but I digress. :)
In any case, this whole discussion about HP/Armor/Resists is fascinating and I'm just reading the differing points of view with great interest. Thanks to all so far who have offered your views! Keep the discussion going! :)