On the face of it, a nine-mana creature, no matter how cool, is pure Timmy territory unless the environment is set up in such a way as to support long games with big mana haymaker plays (say, early to mid-Kamigawa block play). Even with ways to cheat them into play, big creatures need to be truly exceptional to make the cut.
Consider Reya Dawnbringer, who for nine mana is sort of a Debtor's Knell stapled to a 4/6 flyer. Cheating one into play early in a reanimator strategy may seem powerful, especially since a reanimator deck probably has good tools to ditch additional powerful creatures into the yard...except that she's going to immediately eat a removal spell that's been held back explicitly for that purpose.
And that, of course, is the issue with many "one big critter" reanimation strategies in modern Magic. With reanimation in Standard pushed back away from abusively early appearances to more reasonable slots in the turn four to five range, you can't simply chuck something gigantic and hideous into play and hope it makes it all the way. This is why the most recent Standard reanimation successes have hinged on card advantage, whether that involves reanimating token generators (a la Torrent decks) or from bringing back card advantage generators (a la early Mannequin or more recent Calderaquin builds).
However, the namesake angel of this post offers the possibility of "big single creature" reanimation as a valid strategy once again. Let's take a look:

In addition to naming an angel after my friends' daughter, Wizards has, depending on what comes our way in terms of reanimation, given us a pretty solid "eggs basket one" (as Rich Hagon might say) reanimation target.
Take a moment to consider decks you've seen in the last year or two. How varied are their removal options, color-wise? Looking at the impending Alara-Zendikar Standard, we already see strong suggestions that people will consider mono-color builds, and even if they decide to go multi-colored, a lot of their removal that could potentially deal with a 7/7 will live in the same color brackets (Path, Bant Charm, and Day of Judgment are all White, for example). Given that, it's entirely possible that a reanimated Iona can shut off all possible ways your opponent has of dealing with it. What with being a flying 7/7, that's tremendous.
All of this depends, of course, on what reanimation appears in Zendikar. Alara block, home of the powerful Unearth mechanic, has ways to reuse creature cards, but no especially effective ways to dump creatures quickly back onto the battlefield from the graveyard. M10 gives us Rise from the Grave, which is okay, but is not as fast as it might be, and can't carry a strategy on its own. So far, Zendikar gives us Emeria, the Sky Ruin - presumably the place Iona is shielding, given her name - which offers up a recurring Iona, but not a quickly recurring Iona.
I'm not one to try and make a deck with roughly a third of a set spoiled, especially with critical components (say, another good reanimation spell) left out of the mix, but I'm pleased at the possibility of "one big critter" reanimation as a strategy, especially if it means that Iona can serve as an effective foil against mono-color strategies.
On an unrelated note, this card has awesome art, and the real Iona's parents are happy that her Zendikar parallel is so impressive.