From BlenderWiki

Consistent UV Editor Behavior

UV Editor behavior acts consistent with that the 3D Viewport. Increases usability and consistency within the UI.

Editing UVs is no different than pushing and pulling verts, edges, and faces around within the 3d viewport at a top down perspective. Conventional UV editors link the modeling controls with the UV editing controls which allow the user to jump right into editing UVs with little to no unexpected behavior or the need to relearn a new set of controls to operate within another window which involves a similar process of vert, edge, and face manipulation. As such:

• Dragging the left mouse should result in a box select.

• Clicking on any vert, edge, face or island should give the user a visual indicator in which to convey action and expectation of action. This would be a transform widget/gizmo with move, rotate and scale indicators, the very same that is used in the 3d Viewport along 2 axis.

• Clicking off to the side or on empty space should deselect in the same manner as the 3D Viewport.

• Does not necessarily have to result in the removal current hotkey driven behavior in regards to grabbing, rotating and scaling UV elements.

By doing so we can increase user expectation while also adhering to a bit of convention. Such changes can be considered as part of the "low hanging fruit" mentioned during the Blender Conference. This change would also bring Blender in line with other major 3d applications and also reduce unnecessary elements of complexity.