If you had Nebo installed on your device prior to the 2.5 release the only change you'll see is access to a number of new features. Everything else will be exactly the same.
iOS users who have signed up to the Insider program are acquainted with the Draft feature and the Lasso which are now available on Android and Windows devices too. Draft enables you to express your thoughts and ideas in less structured way while the lasso lets you select a word or object and move it around in the draft area as you wish.
Nebo users now have access to a User Dictionary which lets you tailor the in-app lexicon to your own professional or academic needs. (Not available with Nebo Free version for iOS).
PDF export is now be available on iOS and Android devices.