AAPL is in a interesting place. (Been adding to it recently.) Like many other tech stocks, after they reported, AAPL's multiple seriously contracted.
AAPL is currently trading with a trailing multiple of 14.7. Barring the multiple seen in January (12.5), 14.5 was a low end range for AAPL toward the second half of 2011. IMO, the 12.5 multiple was an anomaly as investors were forced to readjust to Apple's new growth trajectory.
Prior to the iPad, and when the iPhone was only on 1 carrier, AAPL typically beat their own estimates by 16-24%. Now that the iPad is gaining wide acceptance and the iPhone is available world wide, Apple has been beating their guidance by +40%. (That's sick, but to the victor goes the spoils.) Realistically, they should see a new range, probably low 20s%/high 30s%.
From a trailing PE perspective, a reasonable assumption can be established to allow AAPL to have a trailing multiple in the mid/high 15s. (If a name like IBM can maintain such a multiple, so should AAPL. The only differences between the two companies is that IBM properly uses financial engineering, where as Apple's growth does not merit heavy engineering. Although they did need a dividend to allow an increased pool of funds to play the stock, via dividend funds.)
With a multiple of mid/high 15, AAPL should be trading between 635-to-655. Heck, even if Apple did nothing for the quarter, then assume Apple beat their own guidance by 24% at the end of the quarter, AAPL would have a trailing PE of 14.5 with a stock price of 637.
Basically AAPL will eventually trade near 630-640 as the quarter matures.
From a technical perspective, AAPL is not overbought and chilling near support SMAs.