wide sounding mastering

In mastering, M/S in very handy indeed.
By being able to adjust M and S separately you can adjust an un balanced mix (if you are mastering someones work other than your own and can't go back to the mix to fix it)
I recently mastered a reggae track that had vocals a db or so too low overall and these big stereo keys that came in during the chorus which swamped the vox completely. Everything in a stereo mix that is panned center will be included in the M portion so by slightly increasing M by a db at most (these numbers are made up, I can't recall the exact settings I used sorry) the vox was lifted out some more. You do have to be careful when doing this though as everything else in M, Kick, bass etc will also be lifted so you may have to adjust low eq to accommodate this change. Then I brought the S portion down .5 db or so to drop those keys I mentioned as they were hard L R. Overall The effect is subtle but it can make a good mix great.

I will see if I can find a before and after mastering clip of the track I mentioned above if you are interested in hearing M/S in action. Its not the best example of it by any means but I am happy to all the same.
 
I downloaded Ozone4 today, was looking for something like this. Worked all day with it. I used the CD mastering with exicter preset, for mixdown into the two track wave file. It's pretty cool great compression and leveling if that is what is called. I had trouble getting enough & consistent snare and kick punch. I can just amp those up tracks in the mix and OZONE takes care of it - without any distortion or other side effects. Well that is not entirely true sounds a bit side-chainish if you are listening for it but I'll take it. I didn't want to replace the snare and kick sounds, although I probably should have had a bad snare day when we recorded the drum tracks (new wire was rattling like a ornery snake).

Did an EP and have a cover of Attack Attack sticks. Not quite finished but I can post a *.wav

Oh yeah about mid/side and width generation,etc. There are the tools/effects and plugins, all good stuff... But we recorded two guitar tracks, direct from two separate amps (all tube Traynor 100W head and tube preamp into solid state PV amp). We like the sound of both mixed its good. But it's kind a senseless to add width to one track or to both. I did add chorus to soften the distortion on one side.

Now if I pan each track say 30% Right and 30% Left there is a little bit of space added but not much. The guitar still feels pretty much centered. I added a phase adjust FX to one side and with the slider moved it -20 to -40 and then real width started to happen. So that is a way to easily delay one side and obtain some nice width to suit your taste.