Update: I've posted a sequel where I ran an experiment in a virtual machine to see just how bad it is.
Half a year ago the roadmap for GNOME 3.0 was announced, and it involves a new window manager called GNOME Shell. They plan to have GNOME 3.0 ready for public consumption in 2010, around the release of Fedora 13. I tested the GNOME Shell back then and it was awful; since then, it hasn't improved a lot, either. And I'm not optimistic about where it's headed; I think GNOME 3.0 is going to be a terrible, terrible mistake.
GNOME has been said to resemble Windows 98 - true, its default theme is pretty gray and boring, but GNOME is flexible enough that it can be made to look just like OS X or Vista or anything else.
The KDE desktop environment looks an awful lot like Windows as well. KDE jumped from versions 3.x up to 4.0 about a year ago, and KDE 4.0 looks a lot like Windows 7. But on the whole, the desktop still looks and acts the same; KDE's version jump was a natural evolution of its desktop, not a complete change to something completely new and unfamiliar.
GNOME, not wanting to be 1-upped by KDE's version jump, decided they'd bump GNOME 2.x up to version 3.0 -- and entirely redefine the desktop metaphor while they're at it. GNOME 3.0 with its GNOME Shell has almost nothing at all in common with GNOME 2.x.
Here is a relatively recent article about GNOME Shell, so you can take a look.
But that's not why I dislike it. I just thought I'd give some background first. This is why I dislike it:
GNOME Shell 3D hardware acceleration. What? Let's compare the current desktop environments: Xfce 4.6 and older, KDE 3.x and older, KDE 4.0, and GNOME 2.x and older... all of these desktops can be run on bare minimal video hardware. You know how Windows Vista, and Windows 7, have "Basic" themes? If you run Vista or 7 on a computer that either doesn't have a kickass video card, or you simply just don't have the drivers installed yet, you get to use the "Windows Basic" theme. Windows has a fall-back to Aero.
But GNOME 3.0 will have NO such fallback. If your video card sucks, or you don't have the drivers, you can't use GNOME 3.0 at all. What will you see? You'll see the X11 server crash and leave you at a text-mode prompt. You will have NO graphical user interface at all; you'll be stuck in text-only mode, because your video card must be kickass for GNOME Shell to load.
Most people have ATI or Nvidia cards, you say? Well, it's well known that ATI and Nvidia have proprietary, closed-source drivers; the companies simply refuse to open up their video drivers as free software. And because Linux is a free and open source operating system released under the GNU General Public License, Linux isn't legally allowed to include ATI or Nvidia drivers "out-of-the-box."
So, when you pop in your Ubuntu or Fedora CD to install it on your computer, the installed operating system can not legally contain Nvidia or ATI drivers. Without the drivers, your video card can't do 3D acceleration. If you were on Windows Vista or 7, you would see the Windows Basic theme; if you're on Linux with GNOME 3.0, you'll see NOTHING! You'll be at a text-mode login prompt, and when you log in, you'll be at a text-mode bash prompt. No graphics, no windows, nothing but text.
This wouldn't be the end of the world for me personally, but then again I know a great deal about Linux. I would be able to install third-party software repositories and install the Nvidia or ATI drivers all at the command line; or at least I would know how to install an alternate desktop environment such as Xfce so that I could get a GUI and then fix the video problem manually. But the average user, or newbie to Linux? They'll be stuck.
I'm curious to see how Canonical (the company behind Ubuntu) is going to deal with this. Are they going to stick it out with GNOME 2.x and ignore GNOME 3.0? I imagine that's quite a likely scenario. Because consider this:
Ubuntu is known as the newbie-friendly Linux distro. It's the easiest one to get set up and running, it's easy to use, and when you log in for the first time it even asks you if you'd like to install some proprietary hardware drivers. Ubuntu can't legally install these automatically but it makes it easy for the user to install them afterward.
What if Ubuntu upgrades to GNOME 3.0, a new user installs it on their computer, and the new user can't even get the desktop to load? They have an ATI card and they don't have the drivers installed, and therefore GNOME 3.0 absolutely will not start because it absolutely requires hardware acceleration. They're a complete newbie to Linux, they know nothing about the command line, but they're stuck at a text-mode prompt. Know what they'll do? They'll switch back to Windows and never be fooled again when somebody wants them to give Linux a try!
Of smaller importance, by reinventing the wheel, the GNOME developers are basically starting over from scratch almost. This means that some of the more complicated problems that the GNOME dev team have tackled in the past may come back. Dual monitor support, for example. The jump to 3.0 is quite likely going to be a large step backwards for the GNOME desktop environment.
I am not a fan of where GNOME is heading. And if the GNOME dev team end up fscking this all up in the end, I'll just be forced to use a different desktop environment. Although, I really don't want to have to resort to that...
I love GNOME 2.x. I can not stand KDE. KDE is just completely annoying to use. Xfce isn't too bad; it shares a lot in common with GNOME (they both use the GTK+ GUI toolkit)... but Xfce feels far behind GNOME 2.x - it feels clunky and old-school, and it lacks certain features that GNOME 2 has, such as integrated dual monitor support; for dual monitors in Xfce you'll have to resort to Nvidia's config tool (if you have an Nvidia card), otherwise you're screwed.
Xfce still has a year to get better, and GNOME 3 still has a year to not completely suck in the end. If GNOME 3 sucks and Xfce is still so clunky, I may even just be forced to abandon the Linux desktop altogether and go back to Windows.
Take a lesson from Windows (and literally every single desktop environment in Linux), GNOME 3.0 - don't make 3D acceleration an absolute requirement, and include a fallback version for basic video drivers. Otherwise a really good chunk of your user base will move on to other desktops, or move back to Windows. And if you keep this up, Canonical and Red Hat may even just have to drop you completely as their default desktop environments in their distros, for making life too complicated for the end users.