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 Bristol-Myers Squibb Co. (NYSE:BMY) rallied more than 2% today after BMO Capital Markets upgraded the pharmaceutical giant from market perform to outperform.

So what: Along with the upgrade, analyst Alex Arfaei boosted his price target to $60 (from $56), representing about 19% worth of upside to Friday's close. While momentum traders might be turned off by the stock's steady slide over the past month, Arfaei thinks that it's a good time to jump in given Bristol-Myers' still-appealing growth prospects and seemingly inexpensive valuation.

Now what: According to BMO, Bristol-Myers' risk/reward trade-off is pretty attractive at this point. "We are upgrading BMY to Outperform from Market Perform based on our more positive outlook for the company's immuno-oncology (IO) pipeline and lower market expectations following the recent update on the Checkmate-012 trial... Now $60/share using DCF," noted Arfaei. "Investors should buy BMY prior to ASCO and should not interpret potentially positive updates for MK-3475 as negative for BMY; this market will likely be large enough to accommodate multiple players." With Bristol-Myers still up more than 40% from its 52-week lows and trading at a 30-plus forward P/E, however, I'd wait for an even wider margin of safety before buying into that bullishness. 

Brian Pacampara has no position in any stocks mentioned, and neither does The Motley Fool. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.