I personally keep triple tracked vocal harmony on separate track, in a folder.

Sounds like you found a great solution. I'll concur with Craig that I love Ableton, but comping and multitracking with it will drive you crazy very quickly.

Listen to Craig. He knows what he's talking about.
Layers and Take Lanes are completely different and thinking they are the same will only lead to the frustration you're experiencing now.
Take half an hour and watch the Groove 3 videos on Take Lanes. Seriously.
 

Anderton
Updateing to X3e will make a big difference, but a bigger difference is there's a step that precedes learning how to do comping/takes in X3 - unlearning how to do comping/tales in X2.

Well, I never used X2, I jumped from 8.5 straight to X3. As it turns out, I didn't get a chance to try Grem's method last night, I hope to do it this weekend. I've simplified his suggestion even further, and removed the concept of the AUDITION tracks entirely. I will create three RECORD HERE tracks, sing my takes into each in turn, then audition right from there.
 
Still a big issue for me though: I will be keeping three takes for a part. I want to be able to solo three take lanes to hear the blend, and then swap around different combinations of three lanes to find the final three. When initially auditioning to weed out the obvious losers, I use the lane solo button, but I can't solo multiple lanes, so what I'm having to do is remember which take numbers are nominees as I audition ("ok, 3 is good, now 3 and 4 are good, now 3, 4 and 7.... now 3, 4, 7 and 9"). And then when I'm done listening one by one I go back and have to mute everything that's not a top choice. Really counter-intuitive. How might I approach this instead?

just watch this
https://www.youtube.com/watch?v=jbiRKPYderY
 
then this
 
http://www.cakewalk.com/CakeTV/SONARU.aspx/Get-Started

jkoseattle
I want to be able to solo three take lanes to hear the blend, and then swap around different combinations of three lanes to find the final three. 

Ignore the solo button on the take lane.  Instead, select whatever clip(s) you want.  Toggle mute/unmute with the K key.  You can listen to as many or as few clips as you want this way..

Ah, yeah, muting is a good idea.  There used to be a useful key in 8.5 (Q, was it?) that would make so I could mute all but the layer I clicked on.
 
Of course, with muting I get all confused with the subtle shades of gray Sonar wants me to distinguish between. There's Play Me Gray, then Muted Gray, then Selected Gray. I haven't researched this too much, but can I tell Sonar to make muted tracks a different color other than slightly-lighter-gray-than-if-not-muted gray?
 
Checking out the videos tonight.

Lane Solo should react similar (if not the same) as the old Layer solo.  Except it's one Lane at a time.
 
But you can also Shift+Click on a clip if you just want to hear that one isolated.  The "speed comping" demos make great use of that, jumping from clip to clip and lane to lane.
 
 
Edit: Make that Shift+Spacebar, not Shift+Click.
 

If I were going to leave Sonar it would not be for crappy Ableton. Ableton is only good for live shows. It is not good for composing unless all you use is loops. If it were me it would be Studio One. It is so much like Sonar it is not a far step to go.  However, I don't have issues and problems that other people may have with Sonar. It has been good to me so far knock on this old computer case. 

Seriously. You have to forget how things worked in 8.5 or X1 or X2.
View.
The.
X3.
Tutorials.

rontarrant
Seriously. You have to forget how things worked in 8.5 or X1 or X2.
View.
The.
X3.
Tutorials.

 
 
This can't be repeated enough.