Research In Motion (NASDAQ:RIMM) delivered a superb set of first-quarter figures this week, driving up the post-2-for-1 split share price past $70, and confirming my March suspicion that the stock, despite its high valuation, was worth keeping.

But Fools take note: That doesn't mean Research In Motion is still a great investment. Remember, the best investments promise both potential for shareholder returns and low risk. These days, Research In Motion offers neither.

Trading at 44 times expected 2005 projected earnings, the stock looks stretched. Analysts expect earnings growth in 2004 to be a whopping 230%. That rate should fall back to 40% in 2005 and 30% in 2006. Let's be optimistic and assume sustainable earnings growth of 25%. That translates into a rich PEG of 1.8. On an EV/S sales basis, Research In Motion is trading at more than six times 2006 sales. At these heights, that's no bargain and doesn't offer a lot of room for big returns.

At that price, it's worth taking a look at the risks. The biggest, arguably, stems from a patent infringement lawsuit filed against Research In Motion by NTP Inc. Each day it looks less likely that Research In Motion will reach an out-of-court settlement -- the preferred route, as most lawyers will attest. Nokia's (NYSE:NOK) recent decision to license NTP's patents lends credence to NTP's lawsuit, raising the level of investment risk. If forced to pay a full license royalty to NTP, forecasted earnings could shrink by as much as 20%.

Sure, the company dominates its market. But it's in an increasingly crowded market that includes companies such as PalmOne (NASDAQ:PLMO), Nokia and Microsoft (NASDAQ:MSFT). These players, plus others, are expected to fight harder to knock Research In Motion off its pedestal.

Then there's the revenue risk. Much of Research In Motion's Q1 revenue growth came thanks to big initial orders from a handful of carrier partners -- AT&T Wireless (NYSE:AWE) and Cingular, T-Mobile USA, T-Mobile International, Verizon (NYSE:VZ), Vodafone (NYSE:VOD), mmO2, and Nextel -- ahead of high-speed network launches. This should be a big source of caution for investors. Carriers are building up their Blackberry inventories now, but re-order rates rely on carriers' ability to sell a lot of 2.5 and 3G subscriptions.

Don't get me wrong, I think very highly of Research In Motion. Were I to buy a richly valued, risky tech stock, it would be among the first I would snap up. While RIM is shaping up to be a great company, that doesn't mean you should pay any price for it.

Fool contributor Ben McClure does not own shares of any of the companies mentioned.