Interesting--but not very?
I was curious to play a Theremin, so I'm glad the library has these!

It's a lovely-looking instrument, and the sound is pleasant and clean, but a little boring.

It's fun, at least for a while, to control the sound by waving your hands around in the air.

But after the novelty wore off I lost interest.

You can make warbly swoopy sound effects, but I wasn't able to find much variety there.

You could try to learn to control the pitch and articulation accurately enough to play melodies, and I could see that being a fun challenge, but it would also take a while to really master, and it didn't seem worth it to me for a monophonic instrument without a lot of character to the sound.

But others may find it more inspiring!