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 Applied Materials (NASDAQ:AMAT) gained about 1% this morning after J.P. Morgan upgraded the chip-equipment giant from neutral to overweight.

So what: Along with the upgrade, analyst Harlan Sur boosted his price target to $30 (from $19), representing about 31% worth of upside to Thursday's close. So while contrarian traders might be turned off by Applied's price strength over the past year, Sur's call could reflect a sense on Wall Street that the company's growth prospects still aren't fully baked into the valuation.

Now what: According to J.P. Morgan, Applied's risk/reward trade-off is rather attractive at this point. "We are upgrading Applied Materials to Overweight (from Neutral) with a $30 Dec-2015 price target driven by its solid position in the semiconductor equipment market (deposition/etch/epi/implant), our continued positive outlook on the current Moore's Law–driven wafer equipment (WFE) spending cycle, and improving confidence in the successful completion of the merger with Tokyo Electron," said Sur. "Given a healthy WFE spending environment over the next few years, combined with cost synergies, we estimate AMAT/TEL can generate $1.90-$2.00/share of earning power by FY16." Of course, with Applied shares hitting a new 52-week high today and trading at a forward P/E of about 20, I'd hold out for a wider margin of safety before betting too heavily on that bullishness.