(1) AAPL is definitely overvalued. The current stock price anticipates tremendous growth over the next few years - which may or may not happen.
(2) December/early January is the worst time to sell, and the best time to buy. Mainly because you'd be doing the same thing as everybody else. Lots of people sell in December in order to write off losses, and tend to buy back the same stocks in January. So if you sell now, you miss the big jump that always happens in January.
(3) Allowing your natural gut urges to take over will get you killed in investing. Everyone knows you should buy low and sell high. But what this reallly means is that you should buy when it's going down, and sell when it's going up, which is the complete opposite of what your gut tells you. Your gut tells you when it's going down, get out before it goes too low. Your gut tells you when it's going up, get in and get on the gravy train. The best time to buy is when there's nothing but bad news, and vice versa for selling. Right now, the news is almost overwhelmingly positive for AAPL - iPods selling like hotcakes, etc. Which means it's a good time overall to sell - but I'd never sell this time of year. The good buys in the stock market are where there's been lots of bad news. For instance, Merck is at its lowest price in something like 9 years, but everyone's afraid of buying because of the anticipation of lawsuits re: Vioxx. Mark my words, over the next 10 years it'll have a huge return.
(4) Stock picking is fun, but on average a losing proposition. 70% of mutual funds - which are run by people who do nothing but study stocks - do worse than the indices. For important money, pick an index fund and forget about it.
Dave