If you'll want to roll back - you should be able to follow the instructions again and import the older version of the toolkit (latest v0.x.x release). That operation should work, but generally speaking only forward upgrades are supported.
You do not need to use [UTEditor] attribute anymore! You can safely remove it as it is not being used by anything. I left it in the code just so you do not get any errors. But feel free to remove it when you'll get a moment.
v1.0+ handles the custom attribute UI a bit differently than before, check out the new Custom Attribute docs to learn more about it!