I can't speak for others, but here are my objections to Gnome 3:

1. It is application-centric, rather than window-centric.

For instance, alt-tab tabs between applications, not between windows. This doesn't mesh well with how I work: I want to alt-tab between different things I'm working on, and alt-tabbing gets in the way of this. Often, I'll have a bunch of terminal windows that are very much different things, or a bunch of emacs windows that are different things, and I want alt-tab to switch between all of them, regardless of which happen to be the same application.

Application-centricity also drives Gnome 3's behavior when you click on a launcher icon for an already-running program, and the Gnome 3 behavior is less useful to me than the Gnome 2 behavior.

2. Sometimes I just want a window to get the heck out of my face. That's why having a button to close a window is nice. Gnome 3 gets rid of this.

3. ...but eventually I'll probably want to see that window again, and it's nice to be able to see all my current windows at a glance on the bottom bar. Gnome 3 got rid of this, also.

4. I don't like having multiple desktops (I like to be able alt-tab between any and all of my windows at a time). Gnome 3 structures the whole UI around multiple desktops.

5. I like having my pull-down menus attached to each window. When you have a big screen, or multiple big screens, it takes a long time to scroll all the way over to your primary screen to get at a pull-down menu. (Yes, I know about Fitt's Law. But if you're far enough away from an on-the-screen-edge menu, it will still be slower than a not-on-the-screen-edge menu that's nearby. I don't know where that point happens, but it _feels_ like it happens pretty commonly when you have two 30" monitors and your window is on the secondary one.)

6. I like pull-down menus. They're been a central element of GUIs since 1984 at least. Gnome 3 seems to want to get rid of them, or at least add another layer of clicks to get to them. All to get the amount of "chrome" off the screen, because it supposedly distracts people or something. (Or so they say. I think it's more because they're designers, and they perhaps value aesthetics over functionality a bit more than I do.)

7. Gnome 3 wants to support touch devices, and by their own admission many of the design features are driven by this. This seems like a big mistake to me. I think desktops and tablets/phones are different enough that they need different UIs. Apple seems to agree with me (or I with them, really), and MS seems to disagree. Do you hear a lot of good things about Windows 8?

8. Even if you like the menubar to be at the top of the screen, I don't see how anyone can think that Gnome 3 did this well. They've set aside that whole top bar, and rather than putting something useful there (like, I don't know, maybe pull-down menus?), they leave most of it blank and put a clock right in the middle? And relegate the pull-down menus to a single application menu, so you need any extra click to get to anything? The only advantage of the Gnome 3 top panel is that it looks nice. Which I think is a big reason they did it that way.

9. I know that a lot of these things can be configured to be like I'd prefer them, but why would I do this, when Mate exists? It works like I want right out of the box. And honestly, Linux desktops are generally at least slightly janky in their default configurations. Using some super-customized configuration just makes it that much more likely that something won't work right.

10. This whole "just get over it and move on" attitude about Gnome 3 is based on the false assumption that it's a done deal, that Gnome 3 is the future, and we're all stuck with it. We're not. (And we're certainly not stuck with the Gnome 3 Shell.) If enough people say "no" to the Gnome 3 Shell, it will go away. There are signs of this already: RHEL7 ships with Gnome 3 in classic mode (or fallback mode, or whatever they're calling it this week), which is an attempt to mimic many elements of the Gnome 2 interface. (Most of that mimicry is only skin-deep, but that's another story.) Debian is considering shipping with Xfce as the default interface. Mate is picking up momentum as a viable alternative to Gnome 3. So I don't think it's clear that we're stuck with the Gnome 3 shell, at least in its current form. There's still hope...

OK, that went a little far afield. But those are some of my objections to Gnome 3.