I have to be considered more in the camp of switching back.
I started with Cakewalk when it was Purple and Black and worked in DOS on my 286 or something like that. Maybe it was a 386 by then. I stayed with every upgrade until Sonar 1. I was around for Sound Blobs !!!! I actually liked Pro Audio 9.
Something didnt sit well with me and Sonar 1. Then as VSTs started coming out, I was swayed by the German company. I did VST 5.1, SX1, 2 and 3. I had so many stability problems that I don't think I actually recorded, I just upgraded graphics cards, convertors, PCs... It was a total inspiration killer. When 3 came out and still made my PC crash and I could not get help from tech support (because it doesnt exist), i said "I don't like you and I don't like your horse" (an old texas term that involves pointing but not with the index finger).
I came back at the end of Sonar 3 and upgraded to 4 very shortly there after. Maybe I am off on the numbers. Its OK. I am getting old.
To me there were two main things:
Stability (which I never achieved with Stein)
Support (which I never achieved with Stein)
Also, I found that at the time, I didn't really care that much for the crop of VSTs out. I had a ton of MIDI gear (still do including Modcan Modular (not really MIDI), Synthi AKS (not MIDI either) Prophet 5/10/VS, 2600, Memorymoog, Elka Synthex, OB Xpander, Roland MKS80...)
I can't say that now about VSTs. I have a couple of show-stoppers. But PC technology has advanced to the point that I can run things that sound stellar.
Sonar is almost rock solid for me. The places where it isnt is from the plug in devlopers (arturia being one that still causes me issues).