I've been with Cake since Sonar Studio 6 & have updated all the way to Sonar X1d-X2a.
I also have Studio One Professional 2.5.
Because I do mostly MIDI, I was not as productive in Studio One as I had hoped - definitely not as well as Sonar in that regard.
Studio One would not record nor playback certain aspects of 'advanced MIDI use', where as Sonar had no trouble either way.
So that was a deal breaker for me. I doubt I'll pay for the next update, unless they do the completely unanticipated, and break out some serious MIDI enhancements.
I was also disappointed to learn that Presonus are admittedly not all that concerned with adding/updating MIDI features, and seem to gloss over it at large. There's even a line in their manual - "Look Mom - NO MIDI".
Now that would be the last thing I would boast about!
There is apparently 2.6 coming out in a few weeks, [based on the last Presonus live broadcast with Rodney Orphus], but it seems that us MIDI users are consistently past over in light of other feature and additions.
For those that do mostly audio, I think they would really like it. Stability is excellent.
I
will definitely be checking out the Mastering options & features in Studio one though, as they do look top notch.
In the meantime, I've recently bought Cubase 7.0.5, and I'm really enjoying it so far.
So because of that, that now makes Studio One 2.5 my #3 DAW - out of 3.
But many like Studio One, and it would be easy to see why, once you get familiar with it.