Luckily for the users, not much has changed: the new SDK is almost backwards compatible, so your existing apps will work after just some minor changes. The API is now more consistent with the Management SDK, and we have solved some long-standing issues with link resolution.
If you used one of the older versions, you might want to take a look at the migration guide which contains more details on what we've changed and how these changes would affect your life.
If you never touched this SDK before, this might be a great moment to start. Dive into our new reference documentation – it's been fully updated, too.
Internally our new codebase is now much cleaner and provides us with a better platform for future development and improvements. Apart from that the whole SDK is now much better tested – across multiple browsers and Node.js runtimes.