If I choose Edit > Transform > Rotate in Photoshop and type in 15, the object rotates 15° clockwise.
If I choose Rotate in Illustrator or InDesign and type in 15, the object rotates 15° counter-clockwise.
While clockwise rotation is more intuitive to me, Adobe seems to have adopted a counter-clockwise direction for every other angle (gradients, drop shadows, etc). So I recommend that all angle/rotation tool consistently use a counter-clockwise direction by default, with 0 being horizontal, left-to-right.
From my observations, every tool already follows this scheme except for the Photoshop rotate tool.
Yes the angle (that goes negatively instead of positively from 0 degrees) in layer effects and gradient layers - is not particularly intuitive. But unfortunately it was set up that way in Photoshop 6 I think it was, when they were introduced for the first time. (Maybe it was 5 where the first drop shadow effects were available, I can't remember). But either way, its now more or less 'nailed in' I'm afraid.
It is an example of how important it is to get these things right at the start.
I do a fair amount of 3D work and the axis orientation, direction and angle rotation are different in most apps. Sometimes XY is the ground, sometimes it's a vertical plane. Sometimes Z is the height, sometimes it's the depth... You get the picture.
In CS, it seems the only inconsistent part is the Photoshop Rotate tool. So it shouldn't be too bad to change it. I know clockwise rotations are more intuitive, but counterclockwise measurements are used widely in geometry and consistency is more important to me. If they behaved the same way, I'd get used to the direction faster. But since I switch between Illustrator and Photoshop regularly, I can't remember which rotation is which.