The site doesn't have Windows 11 running on a remote desktop, and is in no way a fully functioning operating system, but it'll give you the gist of the interface (via lifehacker). Besides, it's a great idea for an interactive, hands-on look, beyond the wealth of leaked Windows 11 screenshots out in the wild.
With no need to install anything, you can give the UI a whirl in most any browser—even Safari, for Apple users considering joining the dark side. Wait, are we the baddies? Okay, no, we're the light side.
The site simply presents you with a (somewhat limited) simulation of the Windows 11 user interface, so you can click around and try the OS on for size. Other than being unable to open most programs, for obvious reasons, all that's really missing is File Explorer and tooltips. Everything else is super well done.
You can even open the search widget, Start menu, Edge browser, and the Windows Store to get a well-rounded look at what you'd be missing out on, should you decide not to upgrade or switch.
So, why not try it out? Decide for yourself if the new UI is too much. And if you find you totally despise the Mac-like start menu, don't panic: there's an app for that.