I've got great news for Apple fans. A new beta testing program is open to the public and could give you a chance to help shape the direction of future Apple software.
The OS X Beta Seed Program lets anyone sign up to receive pre-release updates for OS X for testing purposes. You'll be able to use Apple software before everybody else who's not a beta tester. Plus you'll be able to help spot bugs and give feedback about the features you like and don't like.
Update: Now that Apple has announced the impending release of OS X 10.10 - nicknamed Yosemite - you'll be able to test that too. This summer, when you sign up for the Beta Seed Program, you can download Yosemite before the rest of the public gets it in the fall.
Apple has traditionally kept the testing process for its operating systems under wraps, restricting it to professional developers who pay a fee for the opportunity or invite-only candidates.
There are a few catches. You'll need an Apple computer running OS X Mavericks (obviously) and you'll need an Apple ID. Also, any updates you install you'll do so at your own risk. They may contain bugs which could cause damage to your software or hardware which won't be covered under your warranty. That means you had better backup your hard drives!
Also, Apple will passively collect data about your use over the Internet, including location data. It's possible to opt out of this, however.