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 Lowe's Companies (LOW -0.35%) lost about 1% this morning after Goldman Sachs downgraded the home-improvement retailer from buy to neutral.

So what: Along with the downgrade, analyst Matthew Fassler lowered his price target to $51 (from $54), representing about 9% worth of upside to yesterday's close. While value investors might be attracted to the stock's sluggish action in recent months, Fassler thinks that Lowe's appreciation prospects remain limited given his view of slowing growth in housing turnover.

Now what: According to Goldman, Lowe's risk/reward trade-off is pretty balanced at this point. "If past trends are predictive, then fading housing turns would begin to impact demand with a lag, in 2Q/3Q," noted Fassler. "We believe that current forecasts are achievable, but that upside becomes more elusive in the absence of the housing strength that propelled sales and valuation over the past two years." When you couple those housing headwinds with Lowe's 20-plus P/E, waiting for a wider margin of safety certainly seems prudent.