My Rackety's sleeper finally arrived, after a hellacious experience with the courier (never, ever use YODEL for anything). My impressions are somewhat mixed. As a sleeper for an adult, it's fine. Great, even. Soft cotton, shielded seams - very comfortable, and the material is thin and loose enough that it's viable for use in summer. I can see myself wearing this a lot - it's certainly better than my usual summerweight sleeper, which is a Big Foot PJs made of flannel. The rear zip and snap tab isn't difficult for an adult to work (though it IS awkward - this is not a product that you can casually step out of when you need the toilet, so nappies are a must).
However, for it's intended market, I have to say, I'd be disappointed. It's pretty obvious if you look at the Little Keeper Sleeper that a "Houdini Suit" has to fit tightly, otherwise the wearer can simply withdraw their arms from their sleeves inside the sleeper, and interfere with their nappy without ever needing to remove the sleeper itself. Mine is sufficiently baggy, both in the arms and the chest, to make that pretty easy. Now, that's not an inherent defect of the product, but a problem of sizing. The issue is that Rackety's only offers two sizes - small and medium - and they don't specify what the dimensions are on their website. I suspect that the small would have fit more snugly, but it might have been too short in the leg. That's the trouble with adult bodies - there's far more variation. This is something of a niche product for Rackety's, so they haven't invested in a wide range of sizes.
On consideration, I'm going to hang on to this, rather than taking my chances with a small. I don't need a snug fit, and the looseness of this is what makes it comfortable in warm conditions. Realistically, if you want a rear zip sleeper that fits snugly, you're probably going to need to get it custom made.
Of the two sleepers I've recently bought, I would have to say that I prefer the Lands End one. It's snug, warm, and looks juvenile, where the Rackety's one doesn't.