Version 6 brings async/await, a new handler context and major performance improvements to NServiceBus.
Read more about all new features on the version 6 page.
Upgrading from earlier versions?
Take a look at the Version 5 to Version 6 upgrade guide
Want to see all the nitty gritty changes?
They are all on the v6 milestone
What are the API breaking changes?
Here's the API Comparer diff