Pippin Williamson did an outstanding talk this morning at Loopconf on maintaining commitment to backward compatibility for WordPress products.
He goes through a variety of examples of common ways to break backward compatibility, which is very helpful if you’re often not sure how folks are using your plugin.
The Loopconf talks are already showing up on Youtube, including Pippin’s — which is super awesome. If you watch one talk today, I’d make it this one; though I’ve been listening to most of the livestream talks and they’ve been very high quality so far.