Based on my experience, I have to disagree about the cheap department store bikes or even expensive "brick" bikes. We tried to start my daughter off on a Novara Stinger 12" pedal bike (bought used for $30) that weighed 20 lbs. Since she was accustomed to a 7 lb Strider, she had no interest in trying to propel 3 times that weight and we couldn't sell her on the superiority of a pedal bike. At 4, she could pedal around the park, but quickly got tired of riding. She outgrew that bike (I think she was around 44") and we tried a 16" Trek Mystic (the girl's equivalent of the Jet), which was both heavier and less maneuverable--the geometry of that bike is awful. She fell a few times with that bike and we had a very hard time getting her interested again. It wasn't until we picked up a 16" Hot Rock at a thrift store that she really took off with riding at almost 5. She went from riding around the block to riding miles at a time. With my son, we went straight to the 12" Hot Rock and he was riding at 3.5 and as I said above, will ride 4 miles twice a week. We have a friend who bought her relatively small son a 16" Islabike when he turned 5. He rode 26 miles last weekend on the 16"--I can't imagine trying to do that as a 5 year old on a 23 lb bike. Yes, the bike may only last a year and half, but in that year and a half they are fostering a lifelong love of cycling and having great experiences.