A premium version will be available along the free version from now on. Don't worry though, all core features are (and always will be) part of the free version. It only contains GUIs and the ability to change the prefix, for now.

• Almost every line of code was rewritten, and new concepts are being used to more accurately track the sleeping players.
• Time can pass faster, depending on the number of players that are sleeping. Or you can have the time be set to day, as you are used to.
• Required players can be counted in different ways now: by percentage or an absolute number.
• Localisation was added: English, Dutch, Portuguese and Spanish are now supported by default. Adding your own lang file is still possible as well!
• The singular/plural system of lang.yml is now more advanced.
• Debuffs were introduced to punish players that didn't sleep
• And finally, bypassed players can now sleep!!
• bStats is now being (optionally) used to collect some anonymous info
• The core systems have been changed to be way more robust than ever before

That should cover most changes from your perspective but it's very likely I forgot some features. Make sure to check the plugin page as it has gotten a completely fresh look for v3.

Cheers, guys and girls!