I read several reviews including the 2 poor ones on Amazon and still asked my daughter's great uncle to buy it for her 4th birthday. He ordered it from Amazon and it came very quickly in time for her birthday. The cars do need a good "rev up" and it only comes with one car - the first thing my daughter said was that you need 2 for a race - which is a fair comment. She loves it. She can get it to do complete revolutions, and as the track and cars are magnetic they don't fall off. She's learnt about how magnets work and quite enjoys the cars not completing a revolution as she wants them to be suspended upside down.
The track is a little flimsy and sometimes comes apart with exuberant play but is easy for her to put back together. I would also say it isn't a "fast" track and the cars do take time a little time to get around, having said that she got some money for her birthday and we plan to order the new extra track when it comes out.
Overall she's had some great fun with it - as have her friends and parents!