The hard part is over: Microsoft officially rolled out its Vista client operating system today, now it must convince users, who have more desktop options now with Linux and Apple OS X, that the operating system is the way to go.

And Vista, which has been in development for five years, isn’t the only decision on the table for corporate IT as Microsoft also shipped Office 2007 and announced a faux-launch of Exchange 2007, which is slated to be generally available in early December.

Taken together, those three not only provide options and challenges for IT on their own, but together offer a formidable trio of major software upgrade decisions that will require careful consideration. It is the first time in 11 years that Microsoft’s flagship products, which still generate more than 90% of the company’s revenue, have been shipped simultaneously going back to Windows 95 and Office 95.

Back then, the Rolling Stones’s Mick Jagger sang the band’s “Start Me Up” to kick off Windows 95, but the fanfare for Vista's release to volume licensing customers appears to be coming down to just another business decision.

And users are contemplating if they may want to make the upgrades, and more important, why and when.