The S&P 500 (SNPINDEX:^GSPC) roared into August on the back of solid economic data, with the wide-ranging index recording its first 1%-plus move in either direction since July 11. The S&P finished the day above 1,700 points for the first time in its history, and it ended the day at1706.8 points, for a 1.3% gain. A few heavyweights contributed to the positive momentum, as did a sense of improving conditions out of Europe, but there were plenty of lesser-known stocks that helped pull the S&P to its record close today. Let's take a look at three of the best gains today, and determine whether they're truly deserved, or deviously deceptive.

Oil and gas producer Pioneer Natural Resources (NYSE:PXD) was the best S&P stock of the day, finishing with a 12.7% gain, thanks to impressive revenue growth. Pioneer's $1.18 billion top line trounced the Street's $900.9-million consensus, which was more than enough reason for optimism, despite earnings of $1.10 per share falling $0.03 short of the Street's expectations. The company now expects to produce between 174,000 barrels and 179,000 barrels per day for the third quarter, which is roughly in line with second-quarter production averages of 176,200 barrels per day. The company now expects production to rise 14% to 16% year over year for the full year. Right now, it looks like this is very much a momentum play.

For-profit educator Apollo Group (NASDAQ:APOL) came in second in the S&P 500 gains race today, leading a broad for-profit education rally that seems to be driven by rumors of superinvestor Dan Loeb's Third Point taking a stake in the stock. Despite numerous reports attempting to rebut this unverified speculation, Apollo still closed with an 8.2% gain for the day. Other reports pin the pop on Apollo's University of Phoenix retaining its accreditation, but Fool blogger Robert Ciura was quick to point out that this looks like nothing more than a dead-cat bounce. For-profit educators have been walloped in recent months, and with good cause -- Apollo's key metrics were all down by double-digit percentages in its latest quarter. Until Loeb and Third Point confirm the rumors, there seems to be no reason to follow the hype here.

After the dust settled on a fierce three-way fight for third place that took place throughout the afternoon, third-place telecom Sprint (NYSE:S) was the one left standing, with a 7.1% pop at the end of the day. Today's gains seem to be a mix of delayed optimism surrounding the company's second-quarter earnings, which were released yesterday morning, and today's report that it will be one of the launch partners for Google's (NASDAQ:GOOGL) Motorola subsidiary's flagship Moto X smartphone.

The Moto X will launch at a $199 price point, and will be backed by Sprint's lifetime Unlimited Guarantee, which provides unlimited talk, text, and data service as long as the phone lasts. That's not particularly compelling, since most smartphones don't last all that long, but the Moto X's "killer edge" might be its large customizable range of colors. Unfortunately for Sprint, this edge is only available to AT&T subscribers -- Sprint customers will have to settle for black or white. This, too, seems to be a pop of unusual provenance. Perhaps investors simply felt like buying everything today, with or without a particularly valid reason.

Will Friday continue the S&P's successful streak, or will we head back below 1,700 points sooner rather than later? We'll find out soon, but some analysts are getting skittish. Wells Fargo Private Bank regional CIO Mark Doss told MarketWatch this afternoon that the level is a "yellow light," since he was targeting 1,700 at year end. That doesn't mean that everything will soon be undone, but investors should move with some caution, as market-wide valuations have already grown more in the past four years than they have in any other comparable bull market in history.