I have seen that this has been stalled for quite some time, I have been developing the sprite abstraction for my engine and I don't want to introduce a Java-like. I have seen that Walter was searching for a compelling reason for having it, and I think I have one.

For modifying my x coordinate from the sprite I have:

float x(float v)
    {
        this.x = v;
        if(isDirty)return;
        float x2 = x+width;
        //Top left
        vertices[X1] = x;
        //Top right
        vertices[X2] = x2;
        //Bot right
        vertices[X3] = x2;
        //Bot left
        vertices[X4] = x;
        return v;
    }

This is a non trivial setter that I'm using which is currently does a lot or not based on a dirty flag. I dislike using it right now because I would need to do:
sprite.x = sprite.x + 50. This is very verbose, I could even just make sprite.moveBy(50, 0) which is less verbose than that, but this is so java like and I don't want to back right now. Currently my dirty flag is implemented but isn't being used because I'm setting it to true every frame as it is not possible to use properties like that.