Anderton
lfm
If it's automatic Tempo Detection it's cool.
It's not just tempo detection, it's tempo following. If you have a part whose tempo varies, the tempo map will vary. For example, to test it out I played a rhythm guitar part where the tempo sounded like the guitar player was on tranquilizers, then the coffee kicked in, and finally the tempo fell off a cliff to really slow. I was shocked that SONAR (and therefore Addictive Drums) followed it perfectly, although it's important to set Melodyne to percussion mode on really wild tempo changes. If this isn't a major feature, I'm not sure what is 
No doubt, really cool and major for sure.
Thanks for pointing that out.
Anderton
As to VCA grouping, I believe the main reason for its introduction in other programs is for Pro Tools users. Pro Tools used to have several grouping limitations (not being able to group record and input monitor, not being able to group faders with separate outputs, etc.) and PT 7.2 addressed those by adding VCA grouping. However, SONAR doesn't have those limitations, and Quick Grouping took SONAR's grouping one step further. Also, SONAR has had the ability to group ratiometrically as well as linearly, AND do custom grouping curves, for as long as I can remember.
There have been discussions of VCA grouping in these forums and it seems relevant only in specific situations with post-fader effects and busing. However, maybe I just don't "get" it (which is entirely possible) but I don't see anything that can't be done in SONAR with grouping, buses, and/or aux tracks/patch points. As most of the comments about the desirability of VCA grouping involve separate effect levels on drums, I think it might be possible to create a Track Template with all the bus and aux track assignments needed to do whatever VCA grouping can do. That would simplify matters even further.
Maybe we could continue usefulness of VCA on feature request forum - there is one such request by someone. I tried to explain some things regarding sends adjustments to accomodate how volume automation varies.
It's an intricate calculation of relative percentage adjustments of sends to make the portions of wet and dry signals to be maintained to make the total sum sounding the same.
To simplify a bit
Result1=dry1+wet1 and you want Result2 after automation to be -2dB level from Result1 - what should dry2 and wet2 be?
If you set a fader level and adjust send to be right how you want it - and this is never touched throughout the mix - no VCA is needed.
It's the relative movement that start to change how much wet you need.
It's not easy and obvious to see - but normal sends don't fix that. Each fader movement needs a different percentage change of send to sound the same but different level.
If you route both dry and wet return to same bus and automate that bus fader - problem solved.
But as some level it really starts to be not so organized - thinking larger orchestral pieces.
But since the correct VCA implementations(not Samplitude) also allow nested grouping it is very powerful.ProTools 12.2 reinstated VCAs again from ProTools HD not to loose out to competition. Reaper 5.0 introduced it, StudioOne 3.2 introduced it and Cubase Pro 8.0 introduced it. This all happend in last 1-2 years - so I guess you could say it is a trend in music industry.
As someone said, I think VCA originate from analog consoles and automation. And many prefer to call in DCA in the daw world instead.
Someone used to VCA and that way of thinking is probably more attracted to Sonar as an alternative if it exist.
I also recall someone used to VCAs that refer to soloing options that exist.