Windows 10, GTX1080Ti
Broken: 2.79 and 2.8
Short description of error
Scaling objects or mesh elements uniformly using a white circle on Scale 3Dmanipulator is extremely sensitive. Blender by design sets scaling sensitivity based on mouse cursor distance from the active pivot point. The problem is that 3D manipulator is always present exactly where the pivot point is, and that the central white circle responsible for uniform scaling is always in the center of the manipulator, in a very close proximity to a pivot point. Therefore, any attempt to use 3D manipulator for uniform scaling of an object or its element will always result in excessively sensitive scaling, as the cursor will always be very close to the pivot point when uniform scale action begins.
A simple, quick fix would be to enforce "precise" mode (what happens when you hold down Shift key) as initial state whenever 3D manipulator uniform scale is triggered.
This issue is also present in Blender 2.8, which already overhauls the 3D manipulator functionality, so it would be appropriate to include this fix as a part of 3D manipulator improvement initiative for 2.8 project.