This is the way that system software should be architected. Each successive release of OS X has gotten lighter and more efficient. It hasn’t introduced bloat that forces users to upgrade their systems. Quite the opposite: It’s gotten leaner while getting more powerful.
It’s not clear that Microsoft will ever feel compelled to work the same way. It’s got too much riding on it now that the entire PC ecosystem seems to be counting on Windows 7 to drive new a new crop of PC sales.
That’s a pity for the consumer, who shouldn’t be required to shell out for new hardware just to run the newest system software. It’s all the more troubling when the new system software is released chiefly to fix problems with previous system software (think back to Vista’s marketing as being a more secure replacement for Windows XP; now consider Windows 7’s positioning as a faster, less cumbersome Vista. See a pattern here?)
Everything just works (mostly) and os updates are not forcing hardware updates in the majority of cases. Yes, there are a few edge cases and a bit of bugs in the system here and there but nothing, nothing NOTHING like the M$FT crap.