HP's new slate is so back-ordered, new buyers are not promised delivery until next year. Blowout sales, right? Everything's relative. When your production run is but 5,000 units (that's not thousands of units, but units), orders under 10,000 units stagger your capacity to deliver.
By contrast, Apple's first iPad production run was in seven figures, and sold out before it shipped.
Keeping the market Apple has captured will require continued vigilance in maintaining Apple's competitive advantages, and maintaining the features users think they need. Toward that end, I expect Apple to invest in its next generation of Apple-branded CPUs and a mechanism to ensure that users can print without being subject to print-based denial-of-service attacks. Since Apple's only recently seemed to have hired anyone worried about security, and lost its last batch of chip gurus, these things may take some time.