Congrats on picking a winner!
You got in at about $30/share (split adjusted) and now it's at $200/share. In the meantime you got some fat dividends (re-invested or paid out in cash?) Now you're set to get about $2250 per quarter ($9k/year) for just owning the stock. And the dividend will just keep rising. As AAPL shrinks their float (currently 4.5b shares, down from 6.9b after the 7-to-1 split) and diversifies into more sectors, the money will just keep rolling in. What's not to love?
This is the power of the stock market to make middle class people wealthy. Your money has earned you over $500k (round numbers) in 10 years. That's over four years of your income in 10 years!
However, at some point, it is wise to diversify. Look at Enron, WorldCom, Lucent, GM, Delta, MySpace (Rupert Murdoch squandered $500m buying it), or GE (circling the drain), and you'll see once high-flying companies, slam-dunk investments, that are now no longer anywhere to be found. It's hard to pick winners, so lots of people around here will recommend VTSAX to you.
As you might have guessed, I have both AAPL and VTSAX. Since I have a hard time selling AAPL and buying VTSAX, I still own more AAPL than I do VTSAX. I take my AAPL dividends and invest them in VTSAX as a way to slowly balance the portfolio.