I'm not sure it's an improvement, but I think it's working the way it's designed. It's possible it was made the way it is to match the way it works on a PC, which has always worked as you describe (zoom in steps).
If you select the zoom tool, then click and hold the mouse button, (or use the scrubby zoom feature) does it zoom smoothly?
Thanks Noel, but it used to work much smoother, I can't imagine it was changed to this. If so, its a really bad change...
Maybe it works different on a Mac, not sure. I tried selecting the zoom tool as well, same situation.
Think it has something to do with "OpenGL" settings, which I have enabled same way I do in CS4...
You're not the first person who has said this.
But I don't use a Mac so I don't know from personal observation that the scroll wheel normally zooms in steps in Photoshop CS6. I'm only repeating what I have heard.