This thread surfaced while I had been ruminating over giving away my propane burner (used a couple times, not in the last five years), 8-gallon kettle (not used as often as my 5-gallon because the 8-gallon is so heavy), and 9-gallon cooler mash tun. I've used my Mash and Boil twice and it really sells itself. All together, it's a lot less fuss for my 3-gallon no-sparge batches, in a much more compact footprint. The only physical challenge is lifting the basket post-mash, and I got a rowing machine last month to diversify my workouts so perhaps in a while I'll have the "guns" for that not to be as much of a problem. ;-)
Oddly the piece I would find it most difficult to part with is the cooler, maybe because I associate it with the magic of mashing and the delicious bready fragrance that would hit my face as I opened it every few minutes to stir the mash -- even though lugging it around post-mash, getting the spent grain out, and then washing it is not something I miss at all, and I certainly still enjoy the mash in my AIO. There's no rush for me to divest of all this stuff, but there may be a point at which it would be hard to find takers, even as giveaways.
I wonder if the "recruitment" phase for new homebrewers will continue to be the traditional kit many of us started with (I picked up the hobby 12 years ago), and also what the "retention" phase will look like. Cost-wise an AIO is a higher level of entry, but then again there are no $85 rowing machines either. And if you do need to brew outside on a propane burner and don't happen to own a large kettle, the cost differential gets even smaller.