For better or worse, I sold half of my Apple stock this morning. I bought the stock earlier this year around $85, and it's currently at $165. Last week it was at $187, and I thought "I need to put in a sell order around $175" in case it went down, and sure enough it lost $23 while I wasn't paying attention. So this morning I sold off enough to cover my initial investment, and I'm leaving the rest in AAPL for the long term.
FWIW, my concerns aren't as much about Apple as they are about the economy in general. If we are heading into a recession, I can see the iPhone sales taking a hit. If I needed a new Mac I'd still buy one (you know I think it's the best system around), and I've seen from previous downturns that people will still buy luxury things (like iPods) for entertainment during a recession, but I'm not sure the iPhone fits in that category. I think they'll have at least one more good quarter selling the iPhone in Europe, but after that I'm not sure. (Hmm, if I owned one I might know better.) My only other concern about Apple's stock is that their P/E is 42+, and their competitors are in the 20+ range, and it seems like sooner or later that stuff catches up with you.
You can never know when to sell a stock for sure, but those are my reasons for selling 1/2 my shares today.