Fortune's Apple 2.0 blog), who arrived at his guesstimate by tracking the order numbers of iPad pre-order customers. The lion's share—about 120,000— apparently came on Friday, due to "pure overexcited fanboism" (as Tello put it), with demand ebbing on Saturday and Sunday to "only" about a thousand pre-orders an hour.
So, an estimated 152,000 iPads sold in three days...is that good or bad? Well, that figure (assuming it's accurate, of course; Apple has yet to announce any numbers of its own) pales in comparison to the million iPhone 3GSs that were sold during its first weekend of release. On the other hand, the iPad is a whole new product, not a revamp like the iPhone 3Gs, and let's not forget that Apple's long-awaited tablet won't even arrive in stores until April 3.
In any case, if Tello's estimates hold up, Apple might manage to sell more than a million iPads after about two weeks on the market, a feat that (as Engadget notes) would trump the performance of the original iPhone back in 2007. It's also worth noting that Wall Street (according to AppleInsider) was fully expecting Apple to sell 1 million iPads ... in a year, that is, rather than just a few weeks.
Personally, I'm starting to notice interest in the iPad heating up significantly after that first big wave of disappointment. Sure, I was among the many who was initially bummed out that the iPad wasn't mind-blowingly new; now that I've had a chance to think about the possibilities, however (portrait-oriented Web browsing, great magazine and newspaper apps, jumbo-sized video, and a whole new class of games), I'm starting to see ways to fit the iPad into my digital life. Something tells me way may see lines on launch day after all. (And yes, I went ahead and pre-ordered the iPad for myself—the 64GB version, to be exact.)