1) Features: optimize imports, unused imports highlighting and inline variable are beta. I'm really sure that optimize imports can fails in case impoted implicit defs, so be careful.
2) I tried to improve perfomance. This work is not ended, and I'm not sure how it works now. It would be great if you write to me your feelengs about perfomance (I mean if Implicits feature turned off, and it's still should be turned off on big files).
3) Maya M1 has internal problem. If you see exception like this: "Failed to bind stub to AST", it's strictly recommended to you to restart IDEA, because this exception can affect features like go to class. I'm not sure how often this bug can appear, but it can (from last update it should be more often because I tried to improve perfomance throw stubs, which you can see in exception message).
4) Diana update will be later.