NSV: walking flat surfaces to uphill no problem!

When I first started out I could barely walk 3.0 mph on a flat surface without feeling like I was having to drag myself along within 5 - 10 minutes. But I've recently realized that I must have gotten myself in somewhat of a better shape because I can now walk 3.0 - 4.0 mph at a 15.0 treadmill incline or briskly walk up a hilly road without feeling out of breath. Yeah I still sweat but it's not difficult for me anymore and to some people it may not be much but its a good step for me!