I have a treadmill that I have had and loved for over three years. What I love about it is that you not only lose "overall" weight, you see such beautiful muscle development in your legs/butt/waist! I have dropped 40lbs thanks mostly to my treadmill. Two things to be careful of - overuse injuries to knees and ankles - if it hurts, don't ignore it, treat it, and take it easy, or you'll end up with a nice injury and probably a hot date with your local knee surgeon (ask me, I know).
Also make sure you have a pair of running shoes, and a SEPERATE pair of "walking around" shoes. If you use one pair of shoes, you'll have problems with the shoe supports wearing out and you need every bit of support you can get when you're running. Your running shoes need to be about a 1/2 size larger than your foot (but no so large that they are slipping and blistering your heels or toes) because your toes need to have enough room to spread when you roll up onto the ball of your foot. Even in PERFECT footwear, runners have problems with toenails (hugely popular tshirt among runners -"GOT TOENAILS?" ha ha), but if your shoes don't fit you are setting yourself up for major heartache (toe-ache, actually).
Sorry, definitely not any kind of running expert here, but if I can help someone avoid overuse injuries and damaged toenails, I think I should!