There's been a lot of early access controversy and disappointment this year. Whatever your overall attitude toward the practice, I'd argue that Kerbal Space Program is one example of it being done well; with no need for reservations or caveats. It's already a good game, and frequently it becomes an even better one. Now, it's a beta one too.
A few hours ago KSP launched into update 0.9.0—the official designation of the game's beta release. There are over 170 changes found in the full patch notes, but, in a new blog post, the team explain the basics of what it's all about.
"Building upon a long term project that was introduced with the last update’s destructible facilities," SQUAD write, "players will now have the ability to start from the ground up with a basic space center and turn it into a sprawling compound in the new upgradable facilities feature. It’s not just buildings, either. Players will unlock new capabilities and bonuses as their career path progresses."
Kerbals also now have a progression path. As they complete missions, they'll gain experience to unlock new skills. Advanced piloting, science gathering and spacecraft repairs are some of the intrepid astronauts' potential upgrades.
You can see a round-up of changes in the below video, and the full patch notes over at the KSP forum.