Dvorak vs QWERTY
DVORAK and QWERTY are keyboard layouts for the English language.
QWERTY keyboards are far more popular than DVORAK keyboards. Many people do not even know the existence of keyboard layouts other than QWERTY.
DVORAK keyboards allow for more comfortable and swifter finger movements when typing in the English language. This may also affect typing speeds positively, but its main attraction lies in increasing typing comfort and reducing strain on the typists' hands. While the QWERTY keyboard is known for favoring the left hand for more popular characters, DVORAK keyboards are laid out in a manner that facilitates consecutive keystrokes to be executed by alternating hands, and favors the right hand for the more frequent characters.
Keyboard typing speed varies from person to person but it is generally held that DVORAK keyboards allows people to type faster than QWERTY keyboards. However, studies point out that on average the difference is very small.
The fastest typist in the world uses a DVORAK keyboard.
Although the DVORAK keyboard layout allows people to type faster, it is still taught less than the QWERTY layout because of tradition. The speed advantage that DVORAK gives is only marginal, and users accustomed to QWERTY keyboards may take up to a month before their Dvorak typing speed becomes faster than their QWERTY typing speed. Most of that time getting acclimated to the DVORAK layout will be spent typing more slowly than with a QWERTY keyboard, as well, which serves as a significant discouragement.
 Shortcut Keys
Another major hindrance to the adoption of Dvorak keyboards is the ubiquitous implementation of shortcut keys that assume use of QWERTY keyboards. For example, Ctrl-Z, Ctrl-X, Ctrl-C, and Ctrl-V (Undo, Cut, Copy, and Paste, respectively) are all conveniently located on the bottom row of the left hand in the QWERTY keyboard. Changes in layout and the effect they have on issuing commands via keyboard become still more dramatic with applications such as Emacs and Vim. However, with time and practice, the relocated shortcuts can become second nature too.
Many programmers report that even if Dvorak is better suited to English language descriptive writing, in software development a QWERTY keyboard is often much more suitable to fast, efficient, and comfortable typing. This is in large part because of the fact that programming languages tend to favor different key usage frequencies, especially for special characters that have important meaning in a given programming language.
 Keyboard Driven Software
The widespread community of users of vi-style editors and other applications designed around the same basic input UI philosophy (including the xombrero browser and vi-like keybinding extensions for Firefox and Chromium such as Pentadactyl and Vimium, respectively) favor QWERTY because of the implicit dependence on the keymap in the design of the interface. For instance, the h, j, k, and l row of keys on a QWERTY keyboard correspond with the left, down, up, and right movement actions in command mode of vi. In fact, because vi was originally designed in a keyboard layout somewhat different from modern QWERTY keyboards, it is not uncommon for users of vi-like editors (notably including Vim) and other vi-like software to change their keymaps to rearrange placement of Esc, Caps Lock, Ctrl, and/or Tab keys.
Similar loss of efficiency may apply to other keyboard driven software that is not as explicitly vi-like when the user switches to a Dvorak keymap, such as the Mutt mail user agent. Even GUI software that makes use of significant mouse use, such as many MMORPGs, implicitly rely on an assumed QWERTY keymap for such things as keyboard-controlled movement (often using w, a, s, and d keys for forward, left, back, and right, respectively, in default configuration).
Adjusting such keyboard driven software to accommodate the differences in keymaps between QWERTY and Dvorak can be a nontrivial undertaking, especially when a single user has need to adapt several different applications' configurations to the new layout, and when a single user must accommodate multiple computers.
 Multiple Computers
In addition to potential issues with carrying software configurations to accommodate the Dvorak keymap across multiple systems, configuring multiple computers to use the Dvorak keymap can prove problematic for some users. This can be especially confounding in cases where some of the computers in question may be used by multiple users, where not all users wish to use the Dvorak layout. For ease of transfer of typing skills across multiple systems, then, many people may prefer to stick with the QWERTY layout, effectively a "default" for the western English-speaking world at present.
 Regional Differences
Users of British English should note that the Microsoft Windows environment does not offer a Dvorak layout with the pound and euro currency symbols. To be fully effective, users in this locale should install a .dll file created by the Microsoft Keyboard Layout Creator tool.