I've got a late 2007 Macbook, and before that, a G4 Powerbook, which I both bought too close to their initial model releases, only to be humbled by new refreshes with better processors and hard drive space,...
if I have learned anything from Apple in the many years I have used their (numerous) products, it's that waiting even 6 months can save you money, and even get you a better product!
If you think waiting puts you ahead of the game, I think you are mistaken. Granted, if you're considering buying a computer on a Monday knowing they're coming out with a refresh or new model the next day, yes, you should wait. Otherwise, for the most part, you're just chasing your tail.
If you buy a new model right when it comes out, yes, chances are there will be updates in 6 months. But if you wait to buy until the new model is 6 months old, another 6 months later there will either be another refresh, or another new model. It never ends. It's like trying to jump onto a moving merry-go-round. Eventually, you just jump and enjoy the ride.
From a resale standpoint... If you buy the last refresh of a model AFTER the new model comes out, you can get a decent machine at a decent price, but within a year or so it will already be old news in terms of resale value. I am first hand witness to this, as used 12" Powerbook prices plummeted after the release of the newest Macbooks. I lost over 50% on my Feb '06 12" PB, the very last incarnation, the fastest one they made, spec'd out to the max. Maybe most people don't care about resale value, but for me it's a factor in the price of every new computer.
The only real way to stay ahead of the game, in terms of resale value vs. keeping up with the latest tech, is to buy the last refresh of the old model right after a new model comes out, then sell it 6 months later while people still remember what it is, while its specs are still relevant, and while it's still in good shape. Of course, this means a new computer every 6 months, which few can afford, but many would love.
