Breaking change Add the passing on an explicit Registry to all calls to createType as well as all codec classes. If you are upgrading form an older version, use the migration guide to walk through the changes required.
Breaking change The metadata classes have been moved from @polkadot/types into @polkadot/metadata. If you explicitly create Metadata classes, you now would need to do so with the import Metadata from '@polkadot/metadata'; This is a decorated class, where the previous metadata is now available on Metadata.metadata, alongside decorated consts.*', tx.* and query.*.
Breaking change Session Keys defaults to 4 keys now (Substrate master), depending on your node config, you would want to override with e.g. Keys: 'SessionKeys3' (1, 2, 3, 4, 5 & 6)
Breaking change ValidatorPrefs now default to the new percentage commission model, to use the previous validatorPayment, you can override with ValidatorPrefs: 'ValidatorPrefsTo196'

Changes:

api.derive.* now has built-in memomization
Various fixes and cleanups to api.derive.* including era length progress and vesting calculations
Aligned all types with the latest Polkadot & Substrate, including Kusama CC3
Support for Metadata V9, which adjusts the hashing methods of storage entries
Support for Metadata V10 (still un-released), which includes prefixed map support