I don't care what anyone thinks about Channels Tools, and I don't care whether they use it or not. I keep responding because what I do care about is those for whom this would be the perfect solution to a music production problem, and might pass over it either because they didn't understand how to apply it, or took comments about CT not doing much at face value. As has been pointed it, CT offers several different functions but here I'm talking only about using the width and pan controls for precise imaging in the stereo soundstage.
 
The reason why I find Channel Tools crucial is that 99% of what I track is stereo. Even something as seemingly simple as tambourine is stereo because I incorporate the room. Sources that are truly mono, like vocals, often end up in stereo due to processing.
 
With stereo the channel panpot becomes a balance control. Leaving the Pan control centered and instead using Channel Tools to provide precise stereo width imaging independently for each stream from the stereo source is extremely helpful, while placing each stream to cover a precise portion of the stereo soundstage can improve a mix's clarity. 
 
If you don't work that way, the width control won't seem to do much. If you do, the width control avoids what I did pre-Channel Tools, which was building on the Pro Tools paradigm by splitting the stereo into two mono tracks, then copying each mono track into two channels for independent control over width for each stream (four channels total - a PITA).
 
I had to do this a lot with the Antonio Soler and Bach solo harpsichord projects I recorded with Kathleen McIntosh. We both preferred close-miking the harpsichord, so I miked the high and low strings independently. With the low mic, the L channel would pan full left and with the high mic, the R channel would pan full right. I could then use the low R channel pan and R left channel pan to place the "split point" for the keyboard in the precise middle of the stereo image, and/or weight/overlap the images toward the center so it sounded like you were sitting in front of the harpsichord compared to the more exaggerated stereo obtained by using two mics (which could be addressed only partially by using two stereo tracks with conventional panning). Doing very subtle manipulations on an almost subliminal level of the stereo placement to match particular pieces, and even doing extremely subtle changes between movements, prevented having a "sameness" throughout the CDs yet retained the harpsichord's fundamental sound and character.
 
You could probably come close by using two stereo channels and playing with the pan and level controls instead of breaking it into four channels, but there's significant interaction among the controls ("okay, now the right channel seems louder, so I guess I need to increase the level of the left, then group them and bring them both down a bit..."). It's much more convenient and flexible to be able to do all that with a plug-in on a single track compared to splitting, copying, and creating additional channels, or manipulating pan and level with two channels.
 
Here's a simple experiment so you can hear how I used this with material like Kathleen's.
 
1. Load the Grand Piano 1v 4th into Dimension Pro. This is a stereo piano with low notes weighted toward the left, and high notes weighted toward the right.
2. Play a part that covers the full range of the keyboard.
3. Insert Channel Tools. Play around with the Pan and Width controls, and you'll hear how easy it is to manipulate the stereo image to weight the keyboard however you want - make it more stereo, make it more mono, emphasize the lower notes, the higher notes, etc. etc.
4. After you get a sound you like, copy the track, split it into two mono streams, and put them in different channels. Now try to use the channel amplitude and pan controls to duplicate the sound you obtained in (3), and you'll see/hear how Channel Tools make the process so much easier.
 
So how did the critics react to the recordings? I must have done something right...
 
Padre Antonio Soler Sonatas 
"This is probably the finest recording of selected sonatas of Soler that I have heard; indeed, I find it even more satisfying than the fine performances on a modern piano by the esteemed Alicia de Larrocha." 
Victor Hill - The Diapason
 
Kathleen McIntosh plays Bach 
"The playing is fresh and insightful, eager and probing... The French Overture proceeds with perfect poise... while the Fantasy and Fugue in A minor is like listening to McIntosh build a palace of sound...Highly recommended." 
Craig Smith - The Santa Fe New Mexican