This storyline is perfect. Now I'm not talking perfect as in "Greatest Storyline of all time" or anything, but it's perfect in the sense that it was a logical, sane, rational progression and can help both superstars remain fresh with the crowd. This is actually a more positive version of Legacy breaking up (Legacy's breakup wasn't terrible, just could have been better)
Pros for Miz:
Gives him time to further advance his promo and in-ring abilities, without damaging another top tier star's reputation
Gives him proper airtime on Raw
He gets to verbally go toe-to-toe with someone who also has decent (and a bit unpredictable) mic skills.
Miz will come out the victor
Gives more time for 3rd party star to become free to feud with (like Morrison or Kofi)
Pros for A-Ry:
Gets to run a program with who is considered the top heel on raw.
Will get a good amount of in-ring time.
Solidifies his position (after his screw ups from 2010, Early 2011)
Increases his mic-skills with another talented talker (rare opportunity in the lower-mid card)
Strong Initial Solo Push (Post NXT)
Pros for WWE Universe:
It's fresh and wanted (Strong Breakup feuds are fun, but far between in Today's WWE)
Allows someone else to be in the WWE Title Picture (R-Truth among others)
Riley is noticeably physical stronger and taller than Miz, thus more beat-downs, and revenge beat-downs by Miz (beat-downs = crowd pops)
It was a logical progression (Too often in WWE Storylines are there massive plot holes and omissions, or it's a botch breakup like the Hart Dynasty)
Riley's New, all things considered he'll be a fresh superstar with a different move set who will be displayed on Raw regularly for awhile.
This should be fun for the month or two it lasts.