While Microsoft's Zune may have briefly toppled Apple's iPod from the top of the Amazon.com bestseller's list, US customers are having a hard time getting hold of the new version of the product.Amazon briefly showed the last-generation Zune as its best-selling MP3 player earlier this week. Essentially it appears that a steep price discount on the superseded product had inspired bargain-conscious US shoppers to buy one of Zune's so-called 'iPod-killers'.While that report attracted lots of publicity, it did ignore that Apple had no less than 15 slots in the top 25 list - Microsoft clearly has some way to go to regain lost ground in digital media.Now the Zune 80, the Apple competitor's top-of-the-range Zune player is already sold out and in limited supply across US retail outlets. The 80GB device includes Wi-Fi and an FM radio, but was pretty much unavailable - just in time for Thanksgiving, which took place yesterday.Despite strong sales,   read more »