If you've never done it before and you are healthy enough to do it, you owe it to yourself to try HIIT. In my experience, it burns much more calories in much less time. If it doesn't work for you, the treadmills aren't going anywhere, and you can do your hour-long trudge. If you'd like to do a little reading about HIIT:
http://www.cyclecambridge.com/Smith-HIIT.pdf