Apple rolled out its own artillery earlier this week when it showed off a series of improvements to its own laptop and desktop computers and debuted the iPad Mini, a smaller and less expensive take on its top-selling tablet. Google will return fire Monday in New York at an event that it expected to introduce yet another smartphone and a larger version of the company's 7-inch Nexus tablet.
Hours after the Windows launch, Apple CEO Tim Cook called the Surface a "fairly compromised, confusing product" that tries to do too many things.
"I suppose you could design a car that files and floats, but I don't think it would do all those things very well," Cook said Thursday on a call to discuss the company's latest earnings report.
Microsoft's decision to sell its own piece of Windows 8 hardware threatens to alienate the device makers who license its software at the same time many consumers could be expressing their dismay and confusion with the redesigned operating system.
In an attempt to help people understand the changes, Microsoft is expected to spend an estimated $1 billion promoting Windows 8.
If Windows 8 is a hit, it could also help lift the fortunes of struggling PC makers, including Hewlett-Packard Co. and Dell Inc., whose stocks have plummeted with the rise of mobile computing.
If Windows 8 is a flop, however, it will increase the pressure on Ballmer.
Although Microsoft is far larger than when Ballmer became CEO nearly 13 years ago, the company's stock has lost nearly half its value as Apple, Google and Amazon steered computing in a new direction.
Restless shareholders could start clamouring for Ballmer's ouster if Windows 8 doesn't shake up the state of the technology market as dramatically as Ballmer envisions.
Microsoft shares fell two cents Thursday to close at $27.88.