There is news on this subject in the Down syndrome world. A study, here showing that babies that train on a treadmill walk 4-5 months before those that do not. I really like what Jennifer over at Pinwheels said about this. I can't really say it better myself.

And then there is Timothy. He is approaching 15 months and he is not walking. I know. Not that big of a deal. But am I ready for him to walk? Yep, yep I am. You see. He can walk, he just won't! He won't because Wil isn't and he does not do anything that Wil does not do. I know - sweet, right? Wil cruises furniture and walks behind a push toy and that is all T will do. T does it really well and is very stable - I have spotted him transferring and standing alone but he plops as soon as he knows he is seen. T, like his brother, will not walk while holding our hands. He does the noddle legs thing. Absolutely refuses to place weight on them. Although now that Wil is showing interest in standing alone and taking a random step we have our fingers crossed that T is taking notes.

Here they are on the playground. Wil went belly first down the slide, so T went belly first down the slide.