With Apple back up above $600 in aftermarket trading, the stock is now up 48% year to date. For reference, below is the performance of Apple's stock on an annual basis going back to 1999. The most the stock ever went up in one year was 202% in 2004, when the iPhone was just a glimmer in Steve Job's eye.
From the beginning of the stock's bull run in 2003 through the end of 2011, the stock returned an annualized 56.8% per year. If the stock rises by that much in 2012 it would end the year at $635.