The Boolean selector doesn’t save correctly (github issue: Blueprint boolean selectors not prompting to save and also not saving in blueprint editor · Issue #13206 · home-assistant/frontend · GitHub)
And the Device selector also doesn’t allow saving removing a device after saving and editing again (issue: Device selector acts differently when deselecting devices (design website) · Issue #12147 · home-assistant/frontend · GitHub).
Relevant use case: I encountered both of these in developing a blueprint recently (NFL game score mobile app notifications ). The boolean was able to be worked around using a yes/no Select selector, which is a little more clumsy but workable. With the device selector issue though, I had to document the problem and advise users to switch to yaml to remove a device, or to just delete the whole automation and recreate.
My particular blueprint doesn’t ask much from the user, but more elaborate ones would make that option pretty painful. I’m sure other blueprint creators have run up against this at some point, and either had to implement workarounds or abandoned a potentially useful blueprint.
Searching github open issues, there are several other open issues on selectors that look like low-hanging fruit for WTH fixes.