I will get started on mixing my next effort in 2 days.. Reading up on this plugin. Would love to know the practical use of it.. 
 
How has it helped with your mixing and/or workflow?
 
Thanks in advance.
 
Shahed

I use it a lot, either to swap stereo channels, or else to widen (by applying a small delay to one side) stereo tracks or narrowing stereo tracks (to make room for things panned more L or R)

I also like the spread controls for adding space to tracks. I wouldn't use it on everything, but it definitely has its uses.

Stereo tools for me too, both fake stereoing a guitar track and actually narrowing true stereo tracks or instruments that are too wide for my tastes.

Is it mostly used on the master bus? 

Widening

Anything that you have recorded using mid-side micing is a lot easier to deal with using the channel tools.
 
Glen

magik570
Is it mostly used on the master bus? 

That would not generally be appropriate.
The idea is focussed widening or narrowing the spread of a specific instrument within the mix.
For instance, many soft synths have a stereo output that may be too wide to sit well. You can use the channel tool to scale that down some.

how would you use it to clean up a reverb send? keep the sounds to sides and cut the middle?

I use it to shift a stereo track to the left or right.  You can't simply do that with the pan control.  For example I like to have my Hammond organ sound with a Leslie in stereo but not spread out across the whole stereo field. I like to have it sit more to the left .  With the channel tool, you can do that but still keep the stereo spread.