rabeach
some of the synths that ship with sonar have randomizing parameters if you record just the midi each time you bounce the audio it will be different. this is because these randomization parameters are not recorded in midi. those that record live using synths with the randomization parameters engaged never hear what we recorded when bouncing to a track.

+1, I did a video of Z3TA+2 a year and a half ago and had to do physical loopbacks to capture the real-time tweaking done.

Kylotan
Seems like it's super-important for a small number of people with specific synths, and arguably important for the rest of us who don't want to have to work out how to ensure all the relevant automation parameters are being recorded (though I'd suggest simplifying that process would be more useful).

I agree.  I think I will be using it a lot for recording jazz/blues organ in Kontakt.  Your point that it may be especially useful to "a small number of people" is probably accurate.  It does seem like that will be true for many improvements to DAWs these days since they are so mature.  Similar to MS Word making improvements to the equation editor.
 
Cheers.

I think this function becoming available is just a precursor to the deeper feature of assigning any track as an input, which is coming soon.

That's been wanted by much more than a minority of users.

Kylotan
Seems like it's super-important for a small number of people with specific synths, and arguably important for the rest of us who don't want to have to work out how to ensure all the relevant automation parameters are being recorded (though I'd suggest simplifying that process would be more useful).

I think it will also be a killer improvement as regards freezing synths with multiple track output (yet I have still to install Ipswich and check it out) 
 
When using Kontakt 5 with a drum set plus a few other instruments in the same K5 rack, it can add up to 20+ plus Sonar tracks being fed by one synth instance. So far when freezing the synth, all connected tracks were frozen sequentially, thus it took up to a minute per track (on a fast DAW), adding up to 15-20 minutes for the entire freeze (and sometimes K5 crashed at the end and it meant another 20 minutes) ...
 
Now, with the new feature I hope to just arm the synth tracks and push record and "freeze" all the tracks in real-time (i.e. in parallel) by recording the synth output.
 
EDIT: Meanwhile I have tried and run into a problem of not getting all tracks recorded, 2 tracks strangely go missing and I don't know why (http://forum.cakewalk.com/FindPost/3289155)