So far, Marques says, "I'm the only one working on it" and "the implementation never reached a state that would be peaceful for users." Eventually, he plans to release a Live CD with openSUSE and Unity, but he is in no hurry to see Unity become a standard part of the distribution. "I still have some concerns about if it should be implemented in the next cycle or [whether we should wait] for an additional cycle," he says. Evidently openSUSE, like Debian and Fedora, do not consider Unity an urgent priority.
Distrowatch lists 75 distributions based on Ubuntu. About a third of these derivatives exist to provide an alternative interface, so for them the question of using Unity does not arise. However, among the remaining derivatives whose representatives answered my queries, the reasons for not using Unity are almost as numerous as the derivatives themselves.
For some, like gNewSense, the question of whether to use Unity is one for the mid to long term future -- "after the teething issues have been sorted out," as lead developer Karl Goetz says.
For others, like Trisquel, the issue is Unity's need for 3-D hardware acceleration. Since Trisquel -- like gNewSense -- is one of the few completely free-licensed distributions, this requirement is unacceptable to the development team because it often requires proprietary video drivers.
As Rubicon Rodriguez of Trisquel says, "That would keep pushing distributions to forget about freedom and include proprietary drivers as a default." However, free drivers that can run Unity do exist, such as those for Intel video cards, so Trisquel plans to include Unity in its repositories.
Rodriguez raises the question of using the 2-D version of Unity that is currently in development. Yet, even then, he says, Trisquel would not use Unity "as we see no appeal in trying to differentiate our product by copying the MacOS interface (which is worse than GNOME's in terms of usability)."
These sentiments are echoed by several other Ubuntu derivatives. For instance, the developers of Zorin consider Unity unsuitable to their goal of providing a Windows 7-like interface as well as suffering from a "lack of customizability."
More specifically, Tony Sales, who develops Vinux, a derivative designed for the visually impaired, states that "Unity is not yet accessible to a degree where it is usable by a blind user. Ubuntu themselves have acknowledged this by the fact that if you select the blind profile at boot you get the Gnome desktop, not Unity." While open to reconsidering Unity later, for now Sales suggests that users are going to "feel like they are being forced into using something different because the designers decided to change it."
A more detailed critique is given by Artist X's Marco Ghirlana, who gives as one reason for not using Unity that "most of our users are in poor countries and they have no Macs" that might give them some familiarity with the Unity interface.
Ghirlana also cites his own usability testing. "When I tried Unity on computer illiterates, they were less productive and took ages to understand the concepts behind it. When I show them how to use it, they said that it is pretty to see but hard to use."
An even more detailed usability critique of Unity is offered by Stephen Ewen of UberStudent, which plans on staying with GNOME 2. "Unity's design decreases both visual and functional accessibility, which tabulates to decreased productivity," Ewen writes. "That alone is a deal-breaker in light of UberStudent's mission to increase the academic success of higher education and advanced secondary students.
According to Ewen, Unity's positioning of controls, means that "users must constantly travel to the upper-left of their screen to access program menus. This creates problems for people who wish to interact with more than one program at a time."
He also criticizes the main menu's "enormous size" on the grounds that "if one wishes to view many programs at a glance within the sub-categories, Unity obscures the possibility. This means that the brain cannot map as quickly to program categories and subcategories, which again means further decreased productivity." Although Ewen rates Unity as "scant better than GNOME 3," he worries that both new interfaces will only encourage "balkanization" on the Linux desktop.