This post may sound like "Mr. Obvious" to most folks, but I just thought I'd provide some feedback about my use of mix scenes.  I know it has been out there quite awhile now, but it is the kind of thing that has slowly crept into my workflow, as opposed to being a instant, dramatic change.
 
I think the original motivation was to do A/B tests.  That is great, but there is so much more that it can do.  Initially I found mix scenes a little buggy and unstable, so I avoided it.  But these days, it seems to be rock solid and surprisingly fast in switching scenes.  Here are some things I have done recently:
 
I recorded a live big band show with 14 channels.  This had the 5 saxes individually mic'ed, direct lines on bass and piano, mic on guitar, kick and overhead, 2 area mics covering trumpets/trombones together, a separate solo mic for the brass players, and 2 vocal mics.  We had a total of 6 singers who had widely ranging timbre and technique, and the 26 songs covered a wide range of moods.
 
I got a "foundation mix" that sounded good for the instrumentals and saved that as my primary scene.  Then I created minor variations for single singers, duet singers and brass solos, saving each of those as scenes.  And a couple of quiet balled needed yet another mix scene.  That was so easy.  The upshot is that I have the entire show in one Sonar project (actually one project per set), and if I want to do further refinements to the mix later, I can easily get back to the mix I used on each tune.  That is a lot easier to manage than having a separate project file for each song.
 
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Now for a second example.  I have been working on a project that has a concert band playing a new composition march that uses a men's chorus.  We tracked the concert band in the field last November.  That all was easy.  Last night I had the male quartet to my house to capture the vocals.  I used the scenes a little bit for A/B, but that wasn't really needed.  Here's where the scenes will be awesome:
 
We expect this piece will be performed later this year by a different group of singers.  Coming from the Barbershop tradition, they typically learn their music by rote and repetition, not by reading music.  So the composer is requesting 4 edits:
 
#1 - The band and baritone, lead, and tenor in the left ear and the bass part in the right ear
#2 - The band and bass, lead, and tenor in the left ear and the baritone part in the right ear
etc.  I.E.  a different edit for each of the quartet to learn his own part.
 
The scenes will be perfect for this.  I can keep the same single Sonar file and create 4 new scenes per the above, yet instantly go back to my "real" mix at any time.  I know there are other workflows to get to the same result, but this is pretty cool.  I don't think this great feature gets the applause it deserves.

I should have mentioned, I'd be interested to hear of other uses of mix scenes beyond the basic A/B stuff.

I like to mix scenes too I find them way more efficient.
 
cparmerlee... You can do mixdowns based off of your mix scenes too. that option is available in the Mixdown window.

doment500
You can do mixdowns based off of your mix scenes too. that option is available in the Mixdown window.

I am not familiar with that feature.  Are you talking about the Export Video function?  I have not done any video projects in Sonar.

I don't know if it's just me, but Mix Recall doesn't seem to work properly with 3rd-party plugins, at least with Guitar Rig and Valhalla Room, which I used in a recent project. The issue, IIRC, is that if you reload the current scene (or switch to another scene and switch back), all the settings in the plugin get initialized. This didn't happen with plugins that come with SONAR, including TH2. Do you use any 3rd-party plugins? Do the settings in them remain after switching scenes?

Copied from: https://www.cakewalk.com/Documentation?product=SONAR&language=3&help=Mixing.50.html

If your project contains multiple Mix Scenes, you can export all mixes simultaneously.

To export the entire project, go to Edit > Select > All, or press CTRL+A.
               
Go to File > Export > Audio to open the Export Audio dialog box.
              
In the Files of type list, select the desired file format.
              
Enter a file name in the File name box.
              
In the Source Category list, select Mix Recall.
              
In the Source Scenes list, select the Mix Scenes you want to export.
            
Click Export.
 
Rocky

bluzdog
If your project contains multiple Mix Scenes, you can export all mixes simultaneously.

Wow.  That's strong.  I had no idea.
 

icontakt
I don't know if it's just me, but Mix Recall doesn't seem to work properly with 3rd-party plugins, at least with Guitar Rig and Valhalla Room, ...
Do you use any 3rd-party plugins? Do the settings in them remain after switching scenes?

I have not noticed a problem.  Most of what I use was supplied by Cakewalk.  I do occasionally use some Izotope stuff.  I haven't noticed anything resetting.  These days I drop any non-ProChannel effects into effects bins on the ProChannel strip, as opposed to the effects area on the regular channel strip.  I wonder if that makes any difference.

icontakt
I don't know if it's just me, but Mix Recall doesn't seem to work properly with 3rd-party plugins, at least with Guitar Rig and Valhalla Room, which I used in a recent project. The issue, IIRC, is that if you reload the current scene (or switch to another scene and switch back), all the settings in the plugin get initialized. This didn't happen with plugins that come with SONAR, including TH2. Do you use any 3rd-party plugins? Do the settings in them remain after switching scenes?

I've just run into this problem.  I'm playing with stereo position and width and set up two scenes, one using Channel Tools and the other using the NI Replika delay.  Replika does not remember its settings after a switch.  Channel Tools appears to do so, as does R-MIX.  I tried creating a preset for Replika (a "vst2" preset since I haven't figured out how to create a new preset in Replika) but that didn't work either, so it doesn't remember a preset either.
 
I would really like plugin windows to regain the state they were in, so open if they were open when the scene was saved.  It's a pain with just a single plugin to have to reopen its window after every scene switch.
 
Noel wrote in another thread :
 

Noel Borthwick [Cakewalk]
Regarding 1, its really replacing all existing plugins in the tracks being recalled so the old windows have to get closed. I suppose we could consider reopening the windows if they were open previously, once the mix has been recalled completely.

 
Yes please.

cparmerlee
I should have mentioned, I'd be interested to hear of other uses of mix scenes beyond the basic A/B stuff.

There are some more use cases here. Mix recall is quite flexible and can be used many ways.
One thing I do often is to quickly wipe all plugins used in a project and to reset all faders to unity in one go (using reset mix with the appropriate mix recall settings checked).
Also like you I save several alternate mixes in the same project for easy switching.