mixmkr
so... how many hands for synthetic vari-speed?

Lets just call it Vari Speed :)

I'd like to see it added to Sonar, no matter what the name.

I authentically would as well.

Vari-speed has been a much requested feature for years. I guess that it must be difficult to implement, otherwise we would have it by now.
 

My hand is in the air, too. I'd really like to have Vari-Speed. I had lots of fun with it way back when.

I miss varispeed for years.
Even for recording musical effects in half speed.
 
We earn our money with the digitization of tapes and Vinyl.
And also with the processing of digitization, varispeed would be important.
  
 

Another +1 for vari-speed.

I like vari-speed too, but wonder how y'all want to use it. There are several workarounds in Sonar that care of what I'd usually do with vari-speed...for example, I have two main uses for vari-speed. One is to speed up the final stereo mix, but I can do that with the Ctrl-drag time-stretching DSP.
 
My other main use is lowering or raising pitch so I can sing along, then change pitch back to normal to give a different vocal timbre (or allow me to hit high notes, LOL). For this I just do a premix, mute the other tracks, use the transpose DSP on the premix, and sing along. 
 
Granted having a single knob would be nice, especially for "tape stop" effects (there's no workaround for this that I've found), but given how I use vari-speed I find the existing tools sufficient.

I would like to have vari-speed, too.  There are many creative uses for this other than the obvious.  Yet, I can see the challenge in this, considering that it involves time and pitch stretching.  I'm just curious to know exactly how well it works in other DAWs, i.e., is it flawless?

I have requested it for a long time as well. For me, in the old analog tape days, I used it to bring acoustic instruments in tune with other tracks. Bagpipes, bombards, fixed tone flutes and many other instruments are very often not in concert pitch. By altering the tape speed you can bring those into tune.
 
I used to have a Yamaha AW-4416 digital standalone workstation and it had a vari-speed that simply decreased or increased the sample rate. Change the sample rate/track the pesky instrument/change the sample rate back. Worked like a charm. It was the single biggest thing I missed when I switched over to Sonar. 
 
For me, Melodyne or other pitch correction often takes some of the unique timbres of exotic acoustic instruments.