While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Microsoft Corporation (NASDAQ:MSFT) slipped 1% today after Bank of America downgraded the software gorilla from "neutral" to "underperform."

So what: Along with the downgrade, analyst Kash Rangan reiterated his price target of $36, representing about 5% worth of downside to Friday's close. While momentum traders might be attracted to Microsoft's recent share-price surge, Rangan believes that it leaves investors vulnerable to plenty of downside risk.

Now what: According to BofA, Mr. Market is a bit too excited over Microsoft's CEO transition. "The real issue amid downward revisions, flat FY12-14 EPS, and declining margins is that regardless of CEO, investors must grapple with risk of undoing the 'devices & services' strategy of an $80bn behemoth just when a major reorg has already been set in motion," noted BofA. "On the other hand, trying to move quickly with the status quo strategy could burden the new CEO (while integrating Nokia) and disappoint investors." When you combine that uncertainty with Microsoft's price strength of late, waiting for a wider margin of safety seems prudent.