My children both picked up how to ride them in a few days and were fairly proficient in a week (although they cannot use the brake). There were a few spills along the way. Nothing serious though. They always ride with helmets and I've ordered them knee and elbow pads.
I think for 4 - 6 year olds, I would suggest the Barbie scooter or the Hot Wheels scooter. The brake is easier to work and it seems easier for them to balance at first. The Barbie scooter is heavier than the Razor.
pros:
- Low learning curve
- Compact
- If my son gets tired and refuses to ride his scooter home, I can put him (and the scooter) in the wagon. (Try that with a bike.)
- Fun. I tried out the scooter and had a blast. (I'm not the biggest bike fan.) My husband and I have ordered Razor Pro scooters for ourselves.
- Razor A - it was defective out of the box, the mechanism to fold and unfold the scooter would bind. I eventually called Razor who told me to take it back to the store. The new one works great.
- If you hit a high crack in the sidewalk, you might go flying. So far, hasn't been much of an issue for my kids, they don't go fast enough to really biff it.
- Razor A - isn't comfortable for a larger adult. I can ride it (5'8") ok, but it is a little short. I could make do, but my husband who is taller and heavier can't ride it. (Hence the purchase of the Razor Pro which has taller handle bars and a higher weight limit.)
I'm happy with my purchase so far. My children seem to have learned balance and my daughter is doing much better on her bike.