And see in Mick's photo how Thorn Yellow just about rejects dirt!
Upon inspection of my zero-added-lube chain-life experiment, and reading the threads here, which all indicate very great reduction of wear-inducing circumstances inside a Chainglider, I've started to wonder if it is really necessary to use a stainless steel chainring. I went to the Surly stainless steel ring because a) I always buy the best (I don't mean boutique brands, I mean the best objective quality), b) it didn't cost all that much more than a TA or Thorn chainring, c) I was deliberately building a bike that would require zero maintenance or the nearest possible equivalent, and d) part of the zero maintenance strategy was to fit components that would not require replacement in my lifetime. There's an additional reason to fit the Surly stainless chainring which appeared on consideration of the Chainglider chain width specification: the Surly fits beautifully, but I'm sure you can get thin aluminium chainrings if you search for them, and you could use cheaper plain steel. I don't intend to swap out my Surly chainring (and in any event I've laid in a spare), but I mention this for those of you who are put off by the initial cost of the Chainglider and associated replacements to make it work on your bike.
I'm no longer even certain that the high quality KMC X8 chain I recommend (or even its theoretically slightly cheaper Z8 single speed sibling of the same high quality) is necessary inside a Chainglider, never mind the expensive Rohloff-specific X1. Inside the Chainglider, after a distance in which I would deplorably have worn out two Shimano chains in the days when I ran Shimano hub gearboxes with Dutch plastic full chain enclosures, the X8 chain, running only in factory lube, no added lube at all, appears good to go indefinitely. In that case, why not fit a KMC single speed chain from down the list at half the price of the X8? I won't do this either, because I have X8 spare chains laid in from when Chainreactioncycles had a sale, but the logic is striking.
I guess, like everyone who doesn't have experience of it (see in particular Dan's thoughtful questions in the Chainglider threads), on consideration of its form and construction, I expected some dirt to enter the Chainglider whereas almost none does, and for it to provide more interior grinding possibilities to wear itself or the transmission while in in use there appears to be none.
Remember though: my purpose is now, and has always been, a bike as near as possible to maintenance-free. Some of you guys already achieve amazing mileages with open chains. I wouldn't expect you high-milers to double or quadruple your mileages just for fitting a Chainglider, because all it will do is replace the cleanliness of regular chain cleaning and swapping with maintenance-free cleanliness. All you'll find is some cycling time that you previously spent cleaning chains.