I'm not going to comment on whether or not releasing this book only to game stores was a good or bad move by WotC. Given that this book had originally been cancelled, and that it was only resurrected after a lot of consumer feedback, I'm guessing WotC decided that a smaller print run made more sense than a large one, and slid it into their "retailer support" budget or something like that. That's neither here nor there; the book itself is what I'm interested in, here.
First off, if you're a long-time 4e player, you need to know that a fairly big portion of this book is reprints. All the superior implements from PHB3 and other sources are here; the Henchmen and Hirelings article from DDI is reprinted in its entirety; and there's many Superior Weapon reprints. None with the Brutal property, though; I'm guessing the current dev team doesn't like all the re-rolling. In addition, several items have been reprinted from one of the previous Adventurer's Vaults. These old items have new fluff, rarity, and in some cases some tweaked mechanics, but they're still fundamentally reprints.
With that said, there's a ton of great new stuff, too. I'd go so far as to say this is the best collection of magic items released for 4e yet. There are Greater and Lesser versions of favorites like the Flying Carpet and Gauntlets of Ogre Power, and a lot of this book is dedicated to (finally) filling out the magic item rarity system that was introduced in the Essentials line.
There are new base items, and a collection of feats to go along with them. We finally have Flail, Pick, and Polearm Expertise! There are feats which modify the Knight/Slayer/Scout's Power Strike based on their weapons. We have (at long last) superior armors that ... well, I don't know how popular they'll be, but they're nice to have. And Small characters finally have a Reach weapon in the Pike. Another note - all the Picks have the Small keyword, which means that Gnomes and Halflings who pursue weapon-oriented classes finally have an interesting and flavorful option.)
On to the magic items. One of the main complaints about 4e - and I can't say it's unjustified - is that magic items just didn't feel magical. They were boring. I am pleased to say that the items here generally go a long way towards making magic items fun and interesting again. This is especially true for the Rare items, which are just great. None of them look specifically game-breaking, fortunately, but lots of them will be heavily desired by players. There are some great artifacts, too, including a new version of the Jacinth of Inestimable Beauty, one of my faves from the 1e DMG.
The book is more weighted towards Wondrous Items and other non-core-three item slots, which is fantastic. I've been looking for more items like this, since I'm using an Inherent Bonus system in my Dark Sun game and magic weapons and implements can get kinda boring. Consumables are everywhere, including the return - controversially? - of Cure X Wounds potions that can even heal a character who's out of healing surges ... provided they're bloodied, anyway. Given their price, I expect they will be popular.
Anyway, I'm very impressed with this book, and while all of the mechanics will undoubtedly percolate to DDI in short order, I'm glad I snagged it.