Having said that, indexeddb has been very reliable. There are some annoying limitations though. For example, if you want to create an index on a store using multiple keys, you can't specify which key should be ascending or descending.
If you add the PWA to your home page, i.e. install it, then the browser must not clear indexeddb on an update or something. And as far as I can tell, browsers do respect that.
My overall experience building PWA has been mixed. I think it really depends on what app you're making. For a note taking app, where the data can be backed up to the cloud encrypted and synced, I really think a PWA is the best option. But if you want tighter integration with the platform e.g. accessing the file system, then I would stay away from PWA.
Another issue is ios safari which is missing a lot of features for PWAs and I think unlikely to support them in the future. E.g. background sync, offline push notifications, etc.
Are you considering PWA for any particular app?