Recent top stock upgrades from Wall Street analysts can often mean compelling long-term opportunities. When a widely-followed analyst raises the rating or price target on a company, investors pay attention. Such upgrades are usually based on a favorable change in the underlying business, an improving growth outlook or an attractive valuation. Digital Realty Trust (DLR) We start our discussion on top stock upgrades with the real estate investment trust (REIT) Digital Realty Trust (NYSE:DLR), which provides d ...