That's what's called riding with a flat back. Think about it--if your back is curved, then you need to bend your neck even more to in order to keep your head raised, resulting in an awkward S-bend. With a flat back you have pretty much a straight line from your pelvis to the base of your neck, with just a slight rise from the shoulders to the base of the cranium.

Fitting people to bikes and watching them ride, I think there are three reasons for riding with a humped back. First is just lack of flexibility at the pelvis, and that can be corrected with moderate stretching. Second, riders are just resistant to the idea of a nearly horizontal torso, so they straighten up at the hips but end up having to bend over to find the handlebar. These are the ones who buy up all the riser stems. Third are riders who hunch up to shift their weight rearward in order to take it off their shoulders. These folks would benefit from just sliding their saddles back a bit.

Besides a happier spine, another benefit you should enjoy will be increased use of the gluteus maximus (butt) muscles and decreased reliance on the quads.