- Use HTTPS only! Unencrypted requests are no longer supported
- Honor redirects (301 and 303), which is used e.g. from HTTP to HTTPS
- Semicolon as parameter separator is now deprecated, use ampersand instead
- Make sure you have a unique, identifiable User-Agent string
Otherwise the main difference is a lot of new features and bugs that have been fixed. For more information on the changes to the interface, please see the release notes for version 3.
The migration is scheduled to take place some time during the first half of January 2018.