Go ahead and call tablets a fad if you like. Each day brings more evidence that Microsoft's (Nasdaq: MSFT) dismissal of the form factor is ludicrous at best, dangerous at worst. The latest: new estimates that predict slowing PC sales in the face of an increasing appetite for tablets.

Deutsche Bank analyst Chris Whitmore issued the report in a note to clients yesterday, AppleInsider reports. You might remember Whitmore. He's the analyst who said that IBM (NYSE: IBM) is worth at least $200 a share. (I think he's lowballing.)

He also covers the PC market. Yesterday, he lowered his expectations for current-year PC unit sales growth from 9% to 4%, while upping his estimate for tablet unit sales from 40 million to 45 million. Why? Cannibalization. Roughly 30% of foreign buyers of Apple's (Nasdaq: AAPL) iPad planned to use the device as a notebook replacement, AppleInsider says of the findings in Whitmore's report.

That's an astonishing claim. And it explains why, in the same report, Whitmore cut his price targets for both Dell (Nasdaq: DELL) and Hewlett-Packard (NYSE: HPQ).

The skeptic in me wonders whether Whitmore is being too optimistic. My wife has an iPad, and I'd never consider using it to replace my MacBook Pro. My work depends on having a high-function system available to me for hours at a time.

Yet I should also admit that I often beg to use her iPad when I need to pick up the kids from school. With 3G access, I can perform article and stock research while I wait in the car line. I've come to crave the device I once pooh-poohed as unnecessary.

So, my guess is Whitmore is right. Apple's iPad has become a productivity companion for some users, while others turn to the device for mobile gaming or the occasional TV bathroom break. (Seriously.)

Do you agree? Disagree? Let us know what you think about the iPad, Apple's competitive positioning, and the future of PCs using the comments box below.

The Motley Fool recently introduced a free My Watchlist feature that allows users to stay ahead of the curve and receive up-to-date news on companies like Apple or any of its competitors. To get the latest Apple news and analysis, add the company to your watchlist today: