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 analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Digital Realty Trust, (NYSE:DLR) gained about 1% this morning after Deutsche Bank upgraded the datacenter REIT from hold to buy.

So what: Along with the upgrade, analyst Vin Chao raised his price target to $68 (from $56), representing about 11% worth of upside to yesterday's close. So while contrarian traders might be turned off by Digital Realty's price strength over the past year, Chao's call could reflect a sense on Wall Street that its growth prospects still aren't fully baked into the valuation.

Now what: According to Deutsche, Digital Realty's risk/reward trade-off is rather attractive at this point. "We are upgrading DLR to Buy for the first time in 2.5 years as we believe the company is in the early stages of a successful transition into a mature growth company, following a tumultuous 2013, which saw the exit of its longtime CEO, the embracement of an enhanced connectivity platform and an increased focus on the mid-market and SMB segment," said Chao. When you couple that upbeat outlook with Digital Realty's juicy 5.5%-plus dividend yield, it's tough to disagree with Deutsche's bullishness.