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 Comcast Corporation (NASDAQ:CMCSA) gained more than 2% today after Morgan Stanley upgraded the media and technology giant from equal weight to overweight.

So what: Along with the upgrade, analyst Benjamin Swinburne boosted his price target to $63, representing about 19% worth of upside to yesterday's close. While contrarian investors might be turned off by Comcast's solid share-price run in 2013, Swinburne thinks that Wall Street continues to underestimate its long-term growth prospects, giving the stock plenty more room to run.

Now what: According to Morgan Stanley, Comcast's risk/reward tradeoff is pretty attractive. "By investing in its product, brand, and network it has driven consistent 5-7% cable revenue and EBITDA growth and new initiatives like its next gen set-top platform and home security have yet to kick-in," Swinburne said in a report. "Finally, regardless of potential strategic activity in cable this year, we think the stock can outperform peers." With the stock now up about 45% from its 52-week lows, and trading at a 20-plus P/E, however, waiting for a wider margin of safety seems like the prudent move at this point.