Mine is usually slightly off level if you measure from end to end, maybe 2-3 mm lower in the front. I adjust based on feel, and since I rarely sit far back on the saddle, I measure the "level" starting about 2 cm from the back of the saddle. In other words I don't count the last bit of the saddle, therefore the saddle isn't quite level.

Yesterday though I decided I wanted to raise the nose a touch. I haven't done it yet.

With a flatter saddle (no upturn at the tail), it was level.

cdr