Yes, it works.
You can hide Newsstand and it works exactly like those hundreds of posts and tips and videos say it does. We don't know exactly who figured this out -- coverage of the trick is pretty widespread at this point and there aren't exact credits -- but kudos to who did. It wasn't us. (Update: Appears to be from here, and originally discovered by @AnataTenshi Well done.)
Basically, there's a tiny bug in iOS 5 that allows you to stick Newsstand into a folder if you catch it just as you're making another folder. It's a little tricky and takes about 5-10 tries on average to get it right.
Line up three apps: app 1, Newsstand, app 2. Drag app 1 onto app 2 to create a new folder and then as soon as iOS is getting ready to folder 'em, drag Newsstand into the same group. About 80% of the time, this fails. You get a folder with both apps and Newsstand left out in the cold. When you do, just drag both items back out and start again.
But about 20% of the time, Newsstand goes into the folder, and it is for all purposes hidden.
Be aware that the Newsstand item will not be seen in the group icon (see the picture on this post) so if you ever intend to use it, you may have to hunt around in folders to find it.
And one more thing: The other tip? About spoofing the lock screen by going through the Camera roll? Doesn't work.
Thanks to everyone who tipped us about this
Update: Some commenters are warning that you should not attempt to run Newsstand from a folder.