I personally think they are really cool and made this whole drop quite a bit more interesting! They introduce new decorative elements for animated builds like fountains and steampunk pipes and stuff, and they can be used in entity transport of all kinds.
My only disappointment with them so far is that they’re so random to trigger, I wish we had a way to trigger them manually somehow. Perhaps the first time they’re formed, they could immediately spit out a geyser? That would make them piston-activatable.
I completely agree, I think they look very cool and are and interesting addition!
I had the same thoughts regarding making them activatable. I think it would be great if there was a mechanism to make them passive only (like placing a string above the water or something similar?) for e.g. waterfall animations, but activating them on command would be just as helpful. I really hope mojang has these things in mind.