UNIX has a sound philosophy, but it's full of warts and rust. A major update should be considered, especially where security and localization are concerned. Unfortunately, such things are invisible to end-users and only really affect programmers. There's not much incentive to make a better kernel/OS when you can just put more gloss and eye candy over such old designs.
Irishmike: My feeling is that innovation is nothing more than stealing an idea from an open-source project and mainly I too feel that the computer industry is making more or less an appliance for the masses.
Concerning the "theft" of ideas, I usually see the opposite. Just about every desktop for Linux looks and works like a Windows or Mac system. I've tried over ten distros of Linux and about 25 OSes overall, and I've never used any one of them for more than a week.
Ironicly, the only OS I've used in the last 5 years that I found really interesting was an old copy of OS/2 (version 2.0). It was a lot of fun to play with, but certainly not very stable or flexible. I learned a lot of BAD design tips to avoid by using OS/2.

I agree with the "appliance for the masses." Part of the reason why everything looks like Windows/Mac is because the alternatives are trying to appeal to the mass market. Only power users really seek out alternatives.
Irishmike: What is a keen example of what I am talking about is a new feature of Windows (Vista) which looks keenly like an idea that Sun Microsystems had out on their open-source project called Looking Glass. The Windows implementation of "flip" and "flip 3D" looks exactly like Looking Glass.
My feeling is that we should be looking for ways to consolidate information to reduce clutter, rather than find new, flashy ways to flip between windows. Compare Windows Explorer to Total Commander.
Irishmike: What I don't get is why Amiga, Inc or Hyperion don't simply write their own GUI on top of a *NIX base (just the way Apple did) and make it therefore able to run on any platform that the kernel would support?
I think it's because Hyperion seriously underestimated the improvement in graphics on hand-held systems, and were trying to make a really fast proprietary 2D solution with 3D just tacked on, like the original Amiga. Any embedded system powerful enough to have a PPC processor needs more than that, and anything less is going to run on ARM.
Amiga Inc. was on the right track with AmigaDE. Too bad they just didn't release anything that looked like it really was based on a next-gen platform. Slot machines? Come on.
I don't like Java that much, but after seeing a demo of
SavaJe, it's really changed my impression of where we need to go as far as OS design is concerned. I've seen quite a bit of that platform and what it can do. Plus, Java programmers are plentiful. That means a lot to companies that want to build "toy" applications for their products, like games, messaging services, etc.
GreggBZ: We've hit a sort of plateau on so many consumer technologies.
When it comes to tools, yes. I'd prefer only a modernization of UNIX, but a brand new programming language. Programming, especially GUI development, needs to be made much easier.
A few years ago, I read The Mytical Man Month, and I was very surprised to hear the author say (in the 80's), that computers were basicly fast enough to do anything... it was the system architecture and team management that was the problem. Granted, the author began his programming career in the 60's. The longer you work on computers, the more you realize speed is not the solution. I don't think a lot of people really understand what responsiveness means.
Dovegrace: As for the original topic, the only thing I can think of that would impress ME would be a true 3D GUI manipulated by, for example, something similar to Nintendo's old Power Glove...
Given that a sheet of paper is still one of the most powerful and frequently used tools used by man, I'm not sure a virtual 3D environment is the solution. 2D is still the best for data representation. There's a reason why the virtual reality craze died out in the early 90's.
I see most "VR" controllers as short-lived trends. Tablet screens, like on TabletPCs and the NintendoDS, have a huge amount of potential. If early PDA's hadn't been so proprietary and sluggish, they would have survived the onslaught of other trendy gadgets, like cell phones, and evolved into a much more mature platform. I'm disappointed that laptop computers are still so popular.
BTW, the Power Glove was developed by Abrams/Gentile Entertainment.