My son's physical therapist told me that I should get him his first pair of supportive shoes around the time that he starts walking - but he should still spend AT LEAST half of his walking time completely bare foot to help develop the tiny balance and walking muscles.
She also recommended Stride-rite - the little first walker shoes they have there and very flexible, which is important, but also provide some stability. If you don't live near a stride-rite, I think that if you find a shoe that you can almost bend in half (toe almost touches heel) you'll be in good shape.
That said, I think it's better to err on the side of caution and have your lo spend most of his/her time barefoot. I really only used his shoes when we went to the park a couple times a week.
We also love Roobeez!