I'm going to look at the process of selection and manipulation in 3d rigs. The one thing one does the most times in animation is selecting an item and manipulating it on one or more axis. When multiplied up by the thousands of times we perform the action, we can see why a good rig/program will make it as efficient, intuitive and quick as possible to perform this action, while a bad rig/program will do the exact opposite.
The time it takes for your brain to focus your attention on a new item on a screen is close to linear to the distance the eyes have to travel to get there factored by the difficulty of the task.
To try it yourself, get out a stopclock (most mobile phones for instance will have this) or use an online one. (The benefit of using a regular one is that you can take the time with your off hand while clicking the target to get a more accurate time by including your hand to eye coordination with the mouse).
First, find the center S close to the center and then take the time to find the other S
The "Boris" rig from jasonryananimation.com In the Boris rig from Jason Ryan Animation they use a classic example of an "off character selection control"
The benefit here is that the difficulty of the task is very low (your brain doesn't need to analyze the item very much, the controls are quite clearly positioned in an easy to read, 2d representation of the character. If you want, you can position your mouse over an item in the rig, and then check the time it takes to move your mouse over to the representation in the rig and click on it's coloured dot (zoom in on the image to full screen to get more accurate results). The time it takes would be factored a bit by what position the character is in the world view (identifying right and left, what limb it is, how small it is on screen etc). The relationship between distance in full screen (also try dual monitor if you've got one) and time taken should be quite linear.
The further your eyes travel, the longer it takes.
The main drawback of this is that your eyes and mouse will always travel at least a certain distance (off the world view and onto the character picking menu, then usually back to the item's manipulation control, selecting axis, then dragging). The total time for this will always be 'a bit high', but the variation in time taken will be very low, and you get a predictable time efficiency, even though it's quite a bit lower than what is ideal.
The most standard way of rigging is to have control objects, that are the key manipulation points of a character. They are typically positioned logically to what they control, directly on the character. You typically select them with a mouse click and then for instance select the axis of rotation and then drag to perform the rotation. This method is quite direct, as the attention of the brain only needs to shift to the item, click it, then shift to the axis, usually on the manipulator which will typically be on top of the item you have selected which is not that far away, then perform the dragging action. Compared to the item selection mode, this should be the quickest way, and in many cases, it is. As long as the control item in the world view is easily selectable, this is simply the quicker of the two methods to use. Of course though, there is a drawback. The more cluttered the control items become, the more difficult it gets to select the item. Let's say you have a foot complete with IK Toeball, IK Toe, Heel control and forward kinematics toe/toes. It can sometimes get quite hard to select the item you want (especially from some angles) and you get a lot more mis-clicks and efficiency goes down.
An example of a control objects rig where selection has become difficult
There is another, somewhat over looked method which is even faster though. Much faster. This method incorporates setup of controls so that they react by default the most likely way the user wants to manipulate them. This way the control can be set up to for instance, select an object and drag it on a certain few axis in the same go. This way, there's only one mouse click action, the mouse and attention only travels up to the initial control, and after that you're already manipulating. This is by default on any distance at least twice as fast as the other two. A good example of how this works can be found in this old rig test I did for these types of controls (the rigs I use are more refined, but this shows the principle very well) http://www.usefulslug.com/messiahrig/rigtest.mov Another example of how this can be done is animate immediate in messiah: http://www.projectmessiah.com/x4/vids/Animate_Immediate.wmv
Both of these techniques of click-n-drag control suffer the same drawback of possibly difficult selection as with normal control objects, and additionally the possibility that you would want to affect different axis than what is set up. However, both have the option to use the normal transformation controls as well and it's perfectly possible to combine them with the off character selection panel to add some help with selection in problematic cases.
So what's the difference of a few seconds? Why is this important? Well, when multiplied over the amount of times we actually perform this action of selection and manipulation the difference in efficiency of work is quite large. And the action we perform the most, is probably what we would want to be the most efficient. If you want to record how many mouse clicks you do per day, there's a program called workrave you can download for free here which records the amount of mouse clicks and the distance on the screen your mouse travels (seemingly slightly inaccurate for me). It also tells you when to take a break from the computer and has a couple of nice excersises so you're less likely to suffer from CT. (You want your work to be efficient, not health threatening).