Stocks go up, stocks go down -- and so do analysts' opinions of them. This series, brought to you by Yahoo! Finance, looks at which upgrades and downgrades make sense and which ones investors should act on. Today we're looking at the downgrade that just hit Cooper Industries (NYSE: CBE) and, on a brighter note, new buy ratings for V.F. Corp. (NYSE: VFC) and Tesla (Nasdaq: TSLA). Let's dive right in.

Putting a lid on Cooper
First up: Yesterday's announcement that Eaton (NYSE: ETN) will try to merge with Cooper Industries (the FTC allowing) sparked an immediate 25% surge in Cooper's stock price. For investors hoping to squeeze a little more out of the trade, however, Wall Street has just two words of advice: "Dream on." Both KeyBanc Capital Markets and FBR Capital announced this morning they were downgrading Cooper shares to "hold."

What does it mean to you? Exactly what it says. So long as federal regulators don't object to the merger, there's no reason to expect Cooper's share price to fall back. Plus, this deal is great news for Cooper shareholders, who get to pocket $39.15 in cash and pick up 0.775 Eaton shares for every share of Cooper they own. Considering that Eaton is a lot cheaper than Cooper (10 times earnings versus 18 times) and pays a fatter dividend yield, too (3.6% versus 2.2%), if you should be buying anything today, it's Eaton -- not Cooper.

Should V.F. get an "A+"?
In other happy news, analysts at Janney Montgomery Scott upgraded shares of popular clothier V.F. Corp., the company behind such brand names as North Face, Eastpak, and Timberland. Janney says investors are worrying too much about sales trends in Europe. Whatever happens in the Old Country, the real story, argues Janney, is that V.F. is "taking share domestically, further penetrating emerging markets," and widening its profit margin -- all of which put the stock on "a continued robust earnings trajectory over the next few years."

That's not exactly the consensus view, however. In fact, most analysts on Wall Street are looking for only 13% long-term earnings growth at V.F. -- which seems too slow to justify the stock's 17.5 times earnings multiple. After enjoying 44% gains in the stock over the past 52 weeks, one might best use today's upgrade to grab a last few dollars of profit on the way out the door.

Ticket to ride
Last but not least, we come to Tesla. The stock may be enjoying a positive glow of approval from news that founder Elon Musk's other company, SpaceX, successfully lofted a rocket into orbit this morning. It's now en route to the International Space Station. But that's not the main thing driving Tesla higher today. This morning Tesla announced that, having successfully passed DOT crash tests, its new Model S all-electric sedan is ready for prime time and will begin shipping to customers on June 22.

 Apparently this is all analysts at Maxim Group were waiting to hear before deciding whether the stock was a buy. This morning they decided it is, initiating coverage of Tesla with a buy rating and predicting the shares will hit $50 (a 66% gain off of today's price).

Is Maxim right? It's impossible to say for sure. On the one hand, Tesla is deeply unprofitable and burning cash. On the other, it couldn't really be otherwise, considering the company isn't currently selling cars. What the future holds is anybody's guess. Still, with the stock priced at more than 45 times what it expects to earn next year (once, you know, it actually is selling cars), the share price does look kind of steep.

Fool contributor Rich Smith holds no position in any company mentioned. Motley Fool newsletter services have recommended buying shares of Tesla Motors. The Motley Fool has a disclosure policy.
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