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 Stratasys, Ltd. (NASDAQ:SSYS) climbed 3% this morning after Goldman Sachs initiated coverage on the 3-D printing technologist with a buy rating.

So what: Along with the bullish call, analyst Samuel Eisner planted a price target of $146 on the stock, representing about 54% worth of upside to yesterday's close. So while momentum traders might be turned off by Stratasys' year-to-date price weakness, Goldman's call could reflect a growing sense on Wall Street that its prospects are becoming too cheap to pass up.

Now what: According to Goldman, Stratasys' risk/reward trade-off is rather attractive at this point. "SSYS's leadership in industrial printing, focus on organic R&D, and market leader approach to growth positions SSYS well based on our view that the 3DP industry will develop rapidly, though incrementally," said Eisner. "Over the long-term, we believe SSYS will likely exhibit superior risk adjusted returns due to its narrower set of platforms and established leadership position in each of its segments. Current cost structures are higher than some competitors, though we see opportunities for further Objet integration improvements which would ultimately benefit returns." When you couple that positive outlook with the stock's recent pullback, it's tough to disagree with Goldman's bullishness.