Our next door neighbor has one. Their DD is 3 and zooming all over the sidewalks on hers, picking up her feet and balancing and everything. And she's only had it since March. I assume once they outgrow it, they're ready to learn to pedal a real bike.
Re: Strider pre-bike?
It's actually cheaper because it's last year's model. From what I understand,they upgraded a few things.
So, pre-bike is going to be gone soon. Maybe I shouldn't have made this post. The 6 blue ones may be gone before I have a chance to buy them !