Microsoft's surprise deal to acquire Nokia's phone business for more than $7 billion in cash appears to have left investors cold.

Microsoft stock dropped by more than 5% in early trading following the acquisition announcement late Monday night. The stock opened on Tuesday below $32 a share, effectively erasing the remainder of the stock's gains from after Steve Ballmer announced he would step down as CEO in the next year.

Nokia investors, on the other hand, seemed to cheer the deal, sending the stock up by more than 40%.

Benedict Evans, a mobile analyst, noted that the acquisition is likely part of Microsoft's plan to become more relevant in mobile. However, he questioned how much owning Nokia's phone business will help with that goal, other than ensuring that its best existing partner doesn't go out of business.

"Ownership by Microsoft will not of itself change the sales of Windows Phones. If anything, it will decrease them, since it prompts other OEMs to give up on it entirely," Evans wrote in a blog post on Tuesday. "It will not make more developers make Windows Phone apps or more consumers buy the devices. And it does little or nothing for Windows on tablets. Something else needs to change."

Some were even more critical in their assessment. "Had Microsoft acquired Nokia in 2005, we would have thought that to be ground breaking," said Trip Chowdhry, an analyst with Global Equities Research. "Not in 2013, when the Smart Phone Industry is already well defined."

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During an investor conference call early Tuesday, top execs from Microsoft and Nokia laid out their thinking for their deal and expressed plenty of enthusiasm for it. Terry Myerson, Microsoft's EVP of Operating Systems, described the acquisiton as "the single most exciting deal in my 17 years at Microsoft."

Stephen Elop, Nokia's CEO and one of the names mentioned most often to replaced Ballmer at Microsoft, noted during the conference call that the deal will lead to a "unified" branding and marketing effort on the smartphone front and allow both companies to build on the "momentum" for Windows phones.

"We already know each other, we know how to solve problems together," Elop said on the call, referring to how the two companies have worked together since 2011. The deal, he said, "can accelerate the current momentum."

Microsoft will get 8,500 design patents and rights to the Asha and Lumia brands, as well as a 10-year license to use the Nokia brand on feature phones.The longterm goal, according to a presentation on the acquisition for investors, is for the Nokia deal to help Microsoft get 15% of the smartphone market by 2018, up from its current share of about 3%.

"I continue to believe there's enough innovation in devices — unlike some of our investors — that it will be a growth opportunity to the bold, to the innovative who pursue it," Ballmer said on the call. He also noted the deal was a defensive measure to ensure Microsoft didn't need to be too reliant on Apple or Google's devices and mobile operating systems.

Ultimately, the goal — attainable or not — is to move beyond third place in the smartphone market and take on Apple and Google. But as Ballmer put it on the call, "You cannot get to be [number] two until you are three."

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