General experience is that:
*A Hebie Chainglider from the second and third generation (there may be more generations in recent years but those are the two generations I own and see no reason to replace) matched to the specific hub gearbox for which it was made, and the tooth count and width of chainring for which it was made, but which still requires constant fidgeting with it, is incompetently fitted.
*A properly specified and fitted Chainglider is, for practical purposes, silent. I was for my entire life, whichever other professions I practised for a while, a critic of serious music and a designer of ultra-fidelity audiophile speakers and amplifiers, and luxury cars the price of a big yacht, so I'm nuts about extraneous noise. The Chainglider, in my not so humble opinion, is silent enough. If you have to ride in the middle of the night on the painted lines on a smooth road to hear a component, it is silent for all practical purposes.
*Similarly, for all practical purposes except possibly rare extremes, the Chainglider is well-enough sealed. No chain cover is fully sealed; vintage chain cover talk of "oil bath" running would be actionable at law under current legislation and was always a lie before it became a crime. I run my fave chain (KMC X8) for its entire life on the factory lube inside a Chainglider, and still get three times the chain life I got without the Chainglider; zero maintenance or even inspection now that I know it works. I won't pretend that saving two chains out of every three is a big financial deal -- chains are the cheapest consumable items on a bike -- but zero maintenance every 100km is a very big deal for me, and I bet for others too. Per chain in my use, that is five and a half days (45 hours) in which I can do something else more productive than cleaning a chain. Thank you, Hebie, for the Chainglider!
*There's correspondence on this forum about running a Chainglider in a very specific, truly extreme condition, the playa type of desert -- basically a huge plain of concrete mix just waiting for water to set hard -- in which I thought it was possible that the Chainglider would act as a former to set a chain solid in concrete. But that's all theory; it's never been tested. After further years of experience in which, riding in Ireland, which is the "green and beloved isle" because it rains all the time, I never found any sign of wet or even dust ingress in my Chaingliders, I'm not sure about even the playa being hostile enough to call for the removal of a Chainglider.
*Since the Chainglider is so often contrasted with the Gates belt drive, photographs commonly available of Gates installations in use show considerable caking in the hollows between the "teeth" which will require frequent cleaning if the belt is to work optimally, or perhaps at all. That's exactly why one fits a Chainglider or the Gates belt: to avoid maintenance! The Gates belt has to be replaced too, just like a chain, and is bound to cost more than a chain.
*So the belt drive in its current development isn't permanent, it isn't maintenance-free, and it isn't clean (another major consideration for those of us who cycle in street clothes). All in all, I think it is a comparison the Gates Drive cannot win, even at the same price, until it comes with a wider Chainglider to accommodate it. Good luck with getting Hebie to make a Chainglider for the Gates belt (c.f. more correspondence on this forum about getting Hebie to make a 36-tooth front part for the Chainglider).
*Inside a Chainglider of its own, the Gates Drive belt, which is made with automobile camshaft timing belt technology, potentially could reach a lifespan approaching 60,000m/100,000km, like the belts in cars. Even two thirds of that mileage, to allow for the Chainglider not being fully sealed, like the belt cover in a car, would still be spectacular performance.
*"A Hebie Chainglider makes my bike look like a sissy with lily-white hands rides it." Listen up, my old son, women don't like to be handled with calloused hands. You'll thank the Chainglider for soft clean hands, too.
