SAN FRANCISCO (CNNMoney) -- Microsoft CEO Steve Ballmer famously doesn't hold back, and a tech conference on Tuesday proved to be no exception.
Ballmer expressed relief that Microsoft failed to buy Yahoo a few years ago -- and added that "you need to be a computer scientist" to use Android. He made the comments while speaking at the Web 2.0 Summit in San Francisco.
Moderator John Battelle asked Ballmer point-blank: "Are you glad you didn't buy Yahoo?" He was referring to Microsoft's unsolicited $47.5 billion offer back in 2008, which Yahoo (YHOO, Fortune 500) snubbed -- a move that sparked Yahoo shareholder anger and led to co-founder Jerry Yang stepping down from the CEO post.
Ballmer laughed at the question and said: "You know, times change. When you ask any CEO [that type of question] after the market has fallen apart, it's 'hallelujah.'"
With some prodding from Battelle, Ballmer added: "Sometimes, you're lucky."
Still, Ballmer was quick to say Yahoo "still has a lot going for them," including its search deal with Microsoft's Bing. Microsoft's technology underpins Yahoo's search site, in return for a sizable chunk of the site's advertising sales.
Ballmer was less kind to Microsoft's rivals in the smartphone business.
"Why should I buy a Windows phone instead of an iPhone?" Battelle asked.
Ballmer said the Windows Phone 7 difference lies in the user interface: "The notion of putting your own information front and center....it's not a sea of icons."
He acknowledged some of Apple's (AAPL, Fortune 500) strengths, saying "there's certainly some nice things Apple's done with [speech-activated virtual assistant] Siri, but we've been doing the same kinds of things for years."
Google's Android didn't fare as well.
"You don't need to be a computer scientist to use a Windows phone. I think you do to use an Android phone," Ballmer said.
But he stopped short of confirming that Microsoft will develop its own smartphone hardware to go head-to-head with Apple -- and, soon, with Google (GOOG, Fortune 500), if it completes its planned Motorola Mobility purchase.
"We are working very well and very hard with manufacturers to make sure there is a wide range of Windows 8 products," Ballmer said, trying to dodge the question.
Battelle hammered back, asking again if Microsoft (MSFT, Fortune 500) would build its own phone.
"We've been focused on building hardware innovation, and we will continue to do so," Ballmer repeated, laughing. "But thank you for your suggestion." 
