5) Insufficient Distinction on the Dash: The dash in the overview carries two kinds of icons: favorites, and open applications. However, the only visual distinction between the two is that open applications are lit from beneath -- a difference so small that it is easy to miss even when you are expecting it. You can remove all favorites from the dash, but that seems a drastic curtailment of functionality to correct a distinction that should be obvious in the first place.
6) No Panel Applets: In the GNOME 2 series, applets were small utilities that were placed on the panel so you could open them quickly. In GNOME 3, however, the panel no longer supports applets. Rather, they are -- or will be, since conversion appears to be ongoing -- lumped into the general list of applications, where they are far less accessible. While some discussions among GNOME developers suggests that panel applets might eventually return, there is no guarantee that all or any of them will.
7) No View of Open Apps in Workspaces: In the overview, you can see open applications in the dash and the workspace pane. By contrast, in a workspace, for the most part you can't see which applications are open in other workspaces -- nor even the others running in the current workspace, if enough windows are open.
The sole exceptions are a few applications like the Rhythmbox music player, which displays a tiny icon in the lower right of all workspaces while running, presumably on the grounds that you might want to access it from anywhere. Otherwise, you must either switch workspaces or return to the overview to see everything that is running on the system.
GNOME 3 is in its first release, and should see many improvements in the next few releases as developers learn to take advantage of its new opportunities. But, for now, it seems a combination of innovation and sometimes overly rigid application of design principles.
Under these conditions, I suspect that, for most people, the decision whether to use GNOME 3 or to look for alternatives will not be an easy one. Except in rare cases, the decision will probably not be made out of a burst of unqualified enthusiasm or disappointment. To the contrary, many people's decision is likely to be a qualified one, a weighing of features they like against features they dislike.
That is a sensible way to make such a decision at any time. But, in GNOME 3's case, its mixed nature makes such an approach almost unavoidable, at least for now.
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