Days after a Forrester Research report found surprising demand for Microsoft's (NASDAQ:MSFT) Surface Pro tablet -- 32% of professionals surveyed said they wanted the device -- Mr. Softy has sold out of the 128 GB version.

Both online and physical retail stores are now out of stock. In Seattle, some waited up to two hours in line over the weekend to get their hands on the tablet, Geekwire reports. Mr. Softy later told the news site that response has been "amazing" and that the company is working with retailers to "replenish supplies as quickly as possible."

We don't yet know how much inventory Microsoft had to sell, so it's too soon to compare initial demand for the Surface Pro to other high-profile device launches.

Still, if the Forrester report is to be believed -- and it's looking spot-on so far -- Microsoft may have emerged as Apple's most serious challenger in tablet computing. Intel (NASDAQ:INTC), meanwhile, must be thrilled. The chip maker, whose technology powers the Surface Pro, has struggled to win enough mobile business to offset declining sales to PC makers. Microsoft has suffered from the same issue.

Windows division revenue came in at $5.9 billion in the latest quarter, a 24% year-over-year increase but more than $1 billion short of Microsoft's last major release. Windows 7 helped push division revenue to $6.9 billion in fiscal 2010's second quarter. A weakening Windows business is bad news for Mr. Softy.

Surface Pro may be the second wind the company needs. At the very least, the weekend sellout suggests users see it as a competent enough iPad alternative to keep them using the same Windows ecosystem for tablet computing that they use for desktop computing.

A tourniquet designed to tie off bleeding caused by flagging PC sales, in other words. That's a huge win for a business that's spent the better part of a decade under assault.