I personally like it. I have found that in both of my tanks, it settles down a bit after the initial placing of it (but at first, and anytime I've moved it to a different spot in the tank, the needles are a pain in the butt for awhile). I don't use it as a floating plant - I jam it into the substrate... in doing that, i think I've somewhat created the problem of needles floating around when i move it based solely on the fact that the part that's stuck under the gravel will die off. As far as fish eating the pieces of it... I've never seen any of my fish actually eat the needles. I've seen them pick at little pieces of algae when the odd bit starts forming on the plant, and I've seen them take the floating dead needles in their mouths but they spit them out immediately.
I can't honestly tell you if that plant is worth having... just because I like it, doesn't mean that you'll ever like it. And maybe the reason why I don't mind it while you hate it could have something to do with the fact that I'm not bothered by picking the dead needles off the filter intake if they start to accumulate... maybe I've become desensitized to what a nuisance it really is? I guess for me it's not really a matter of "the needles on my Hornwort
are magical and never fall off," it's more a matter of "meh, no big deal... if I see they've accumulated, I just reach in and grab them and throw them out."
Soooo... I hope my endless rambling has somewhat helped put things in perspective... it's maybe not a plant for everyone, but perhaps if you give it another day or two it'll settle down and stop dropping so many needles.