P: What happened to dragging from Illustrator to PS?

Oh, thanks a lot! Now I finally got it!!! Just realized the field "add automatically to my Library" was checked, so that's why all the copied from Illustrator objects they were fallen to the library and I didn't know that. I find this is really misleading! Thanks a lot for the clarification!

Just double click on the smart object to edit.
If you put the smart object into CC Libraries, then it will fail because CC Libraries cannot edit in other apps yet.
If you didn't put the smart object into CC Libraries, then it works like it has since smart objects where introduced in Photoshop.

Thanks, Chris. Sorry, I didn't get it, and it is really important for me to know. So I made an icon in AI then copied it and paste in Photoshop. I don't have the source file with AI icon anymore, how can I then edit this icon in AI again, when I have it only in Photoshop as a Smart Object now? this is my question. And as far as I understand I can't edit this vector icon anymore..or can I ?

You can -- nothing about that has changed.
The only known problem is that smart objects from CC Libraries can't be opened directly in Illustrator due to a limitation of CC Libraries (it's a problem across all applications).

Hey guys, PLEASE tell me please why can't I now open my smart object  from Phin Illustrator in 2 clicks how it was before? How can I open it now? I have a version Photoshop CC 2015.1.2

Still not solved for Mac, and apparently Adobe support can't figure it out either forums.adobe.com/thread/2066028  neither do they believe it is really a problem for more than a handful of people

Yes!!! How wonderful it is to have this back. Please don't ever, ever, ever take it away again lol.
:)

Only copy through clipboard works fine.

I go back and forth from illustrator to photoshop alot. Today when I was trying to drag an object from illustrator into Photoshop, the object would not transfer. The panel highlighted, and the cursor changed to a + sign, like always, but nothing appeared. I did everything the exact same as I have 1000's of times before, but I can't get it to work. I CAN copy and paste objects, but then it puts the object into my Libraries panel.
Why can't I drag and drop anymore?