I just couldn't resist when I saw the comparison being made in
this MSDN blog post between the Explorer in Windows 7 and the Explorer in Windows 8
UI wise that Win 8 explorer is horrible to an end user. Everything and the kitchen sink in your face is absolutely not the way to go about interaction. A lot of different interaction possibilities fighting for attention.
When MS released what looked to be a tablet OS teaser for Win 8, I was hoping they were actually on to something, trying to move forward. Then there were reports of "regular" windows thrown in there as well depending on the application, which sounded like two different interface concepts with different mechanics fighting each other.
Now this. This is a step backwards in interface design. What's even more ironic is how MS in that blog post goes on about a few commands that from user testing seem to be the ones to focus on, only to mix them up and
inlcude the less prioritized ones as well in that horrible ribbon ui.
MS seem to lack interface
designers on the explorer side altogether. They need some new designer blood.
In the mobile world we are moving towards more streamlined interfaces that try to focus on the main content with clear large, and even full screen, menus when needed. Garbage is suppressed. Apple is currently using Lion as a testing ground (EDIT: And Linux as well it seems!

) for how to adopt that to a desktop environment. For better or worse, sure, but they're looking ahead.
That Win 8 explorer interface on the other hand reeks of '90s ui design with bits all over the place. It honestly looks like a joke to me.
It's odd really. MS can bring out some fantastic
concepts but when it comes to
release products it's the same old (on the software side). As if their concept lab exists in another universe. PR wise they even hype up these concept products, only to silently killing them shortly after, with no release. I actually liked what the Courier wanted to be. More so than the iPad. [EDIT: I should perhaps note that I'm not discussing the OS itself, Win 8 might be great, I'm just commenting on what we've seen of the explorer ui and ui talk so far.]
EDIT:
How does Gnome 3.0 on Linux compare to the new UI in OSX Lion?
I've been playing around with Gnome 3.0, and it seems like the designers have a similar philosophy about desktop navigation.
Gnome 3.0 Preview (This is not my video):
http://www.youtube.com/watch?v=joBXc3IGRBw
That actually looks very, very nice. Personally, I don't really care whether a UI concept has been borrowed from another OS or not as long as it's put to good use. The stuff that looks similar to what we have in OS X in that video is elegantly integrated with the rest of the features in a seemingly efficient way, not bolted on for show. Loved the integrated window manager as well - I currenty use Moom for that feature.