"extends the complimentary | [sic] | coverage."
Grammar police stepping in for a citation. Apple coverage is neither compl
Imentary nor free. Warranty/coverage adds on, but does not flatter: is compl
Ementary. Furthermore, there's no free warranty/coverage. manufacturers include warranty/coverage costs into initial retail price as part of the profit calculations. AppleCare coverage extends the initial 1 year PAID retail coverage with an additional 2 years of add-on PAID coverage.
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Word games aside, to answer the original question: I strongly suggest buying AppleCare for all laptops and no desktops.
My personal data supports this without anomaly. AppleCare has invariably reduced the first 3-year cost-of-ownership for my PowerBooks (4 of them), iBooks (2 of them), and my MacBook. AppleCare would have increased my first 3-year cost-of-ownership for each of my my desktop macs: 680x0 (12), PowerPC (9).
Note: my iPod experience does not follow this portable/desktop rule. I still use both my iPods, which continue to function smoothly into their fifth year and beyond.