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 TripAdvisor, Inc. (TRIP -0.52%) rallied 3% today after the online travel company issued upbeat guidance and received a hold-to-buy upgrade from Cantor Fitzgerald.

So what: Along with the upgrade, analyst Naved Khan raised his price target to $94 (from $92), representing about 16% worth of upside to yesterday's close. So while momentum traders might be turned off by TripAdvisor's sharp pullback in recent months, Khan's call could reflect a sense on Wall Street that its turnaround prospects are becoming too cheap to pass up.

Now what: According to Cantor, TripAdvisor's risk/reward trade-off is rather attractive at this point. "We are raising our rating to BUY (from HOLD) as tailwinds from improving shopper monetization, accompanied by healthy double-digit shopper growth (with easing comps in 2H14) and higher conversions yield a meaningful pick-up in TRIP's top-line growth for the remainder of the year while successful transition to meta-search also positions the business for sustainable healthy growth over the medium/longer term," said Khan. "We see prospects for further upside from planned TV ad campaign and newer initiatives (e.g., instant booking, TripConnect)." More importantly, with TripAdvisor shares still off about 25% from their 52-week highs, there might be plenty of upside left to buy into that potential.