@ downix
A lot more than that. Before Windows is released, there are reviews for years ahead of time on various websites. There are streamed videos of how it works. There is a tearing apart of it's inner workings and dissection of every click and mouse movement.
Not years ahead. And anyway, you can't have a "review" before the product is released. You have a "preview" :-)
Longhorn is just starting to have useful information leak out about it, and it's probably going to be released next year. But there's been vapourware information going on about it from reputable sources going on for years.
You don't get a dissection of any OS, particularly Windows way before its release, or even before its release. A few trusted companies/websites are allowed to look but not touch it, only as long as they say nice things about it. I keep my ear to the ground reasonably about Longhorn, and I've only seen the screenshots for it, and some dodgy videos of strangely/dodgy animating windows, and the bizarre "128MB graphics card required to run Longhorn full stop" requirement.
Ok, you find a majorly detailed pre-release of information for any OS and I'll concede on a single point. About Linux, generally you see an errata and new features list when a new kernel is released. Otherwise, distros get p/reviewed, in a "it was easy to install and I quite liked it" point of view. BSDs you certainly don't, and (while I'm not sure on this next point) Solaris I've not heard of such detailed criticism or information coming out pre-release.
Yes, AmigaOS4 should have hit the shelves by now, considering the release of the AmigaOne hardware. If that had happened as intended, then the p/reviews would have come out as they usually do, however it's not finished yet. If you do your homework, you'll find generally that particularly with Windows, previewers are allowed a few screenshots and are allowed to say a few nice things about how great all the new features are, that's about it.
Particularly with the OS4 featurelist, I've never seen anything so detailed pre-release for any OS, and I'd like to see you produce some evidence to support your statement.
One more thing - when was the last time you saw a PUBLIC beta of Windows, MacOS or any other commercial operating system? I think you'll find, as with most operating system releases, that only a selection of people will get betas shipped to them. Just like with AmigaOS. And they probably have to sign NDAs, just like OS4 testers had to.