Is DVORAK worth it?
(if you never used any 10 finger system)?

From what I have heard, no

As everything, it depends. Do you want to use shortcuts (spoiler: you do), then you may have a hard time, since most shortcuts are made with qwerty in mind.

Also if only ever use your own keyboard, it may be worth it. But if semi-regularly need to use someone else's keyboard, it's not worth it

I can see Dvorak making sense if it's the first layout you learn instead of qwerty. A popular Dvorak variant is compatible with the shortcuts for copy and paste and it's not dependent on you using a specific language(like Colemak). But you're gonna have to live with the fact that every stock keyboard and every piece of software is made for a different layout, it'll probably take you months to achieve the same speed you had before, it's not fast enough that the speedup can even be reliably measured if it exists and if you're used to something shortcut-heavy like Vim you might as well roll your head over the keyboard.

I'm using Dvorak since over a decade and have no plans to go back. For the rare event that a coworker wants to type on my system, switching layouts is two clicks away.

It's only a couple percent more efficient than QWERTY and it's a lot of hassle to have a seamless experience. So not really