Matt Brown, an analyst at Cambridge, Mass.-based Forrester Research Inc., said IBM's push to make Sametime open-standards-based will be attractive to customers who want to marry different parts from different vendors to build their IT infrastructures. "That's a pretty significant part of the announcement," Brown said. "They're drawing the line there. For Microsoft, that's not part of their story."

One thing prospective customers will find intriguing, he said, is that IBM plans to support the three mobile communications frameworks, as opposed to Microsoft's focus on Windows Mobile. "Companies are going to find it very compelling when you're looking at an IBM perspective" for mobile users, Brown said. "It's a frontal assault on Microsoft, on the same day that Microsoft announced its unified communications strategy," he said.