My boy is 5 and has been in training wheels for about a year or so. I took them off before but he refused to even try. While riding a few nights ago I noticed he seemed to have "it". He was flying around corners, jumping down curbs and while riding straight the T-wheels didn't touch much. I felt he was ready.
My wife bought him a full set of pads and I had just given him a new Giro helmet a few days before. I think this helped his confidence. Well tonight in a parking lot I removed the wheels. I just ran along holding him by the shoulders, first with two hands then one then none. The shoulders was an idea i got from brown's site http://www.sheldonbrown.com/teachride.html It worked great.
Now I'm gonna spend all weekend riding with him