1. Build anything you want.
2. Play online with friends
3. Advanced wrench events system.
4. User created add-ons
5. Game engine allows for over a 100,000 bricks in a server. Your computer's power may limit that
6. Nice looking graphics. Not amazing next gen, but the game still looks good.
7. Decent community with a good amount of players
someone pick up the slack!
8. It's addictive.
9. You have too much money anyway, am I right?
10. The internet lives here.