I used to have Cubase (VST 5.1-Cubase 3 or 2 - I forget). It was unwieldy and had very cluttered interface. But the thing that bugged me the most was the forum participants. I was treated like an idiot for asking questions - usually about stability and locking up all the time. And there was no customer support back then.
The guys that were the architects behind Cubase wrote the code for Studio One. I think they tried to get rid of bloat and make the DAW simpler.
I bought Studio One 1 when it was released as I was having some issues with Sonar (don't recall), but found it to be immature. I have upgraded the 1-2 and recently the 2-3 for Studio One. It has come a long way.
I know I am missing the serious MIDI editing capabilities of Sonar and Cubase. I hope they develop more tools. I have a couple of awesome vintage synths (memorymoog, waldorf wave and a decidedly non-MIDI Synthi AKS). Plus I have the DSI OB6. I want to be able to record SYSEX at some point.
But I mainly use some drum program (AD2, SSD, Kontakt), some vintage keys (Arturia gets a lot of use) and track guitars, bass and vocals. For that, SO3 is excellent.