And, one more thing, since you mentioned it. It's utter BS that Apple "just works". OSX upgrades are easier because there's a limited amount of hardware they're upgrading from but even under those conditions operating systems upgrades from Apple do go wrong.
Not really, if your computer isn't compatible with the upgrade, Apple won't let you try. The plus side of them making a limited number of configurations is that they know which ones an upgrade will support
