Investment research firm PiperJaffray today reported that its checks of Apple retail stores reveal that Apple is "highly stocked" heading into the holiday season, while third-party retailers are "struggling to replenish" supplies. Reiterating an "outperform" rating, the firm said that the distribution limitations may limit iPod sales and that Apple may not be able hit iPod shipment numbers estimated by some Wall Street analysts. Late last week, 8 of 10 Apple stores had all iPods in stock; however, only 2 of the 20 third-party retailers, however, had all varieties of iPod. Inventory for both the iPod and nano remains spotty...