My mother-in-law bought this for my son when he was about 5 months old and he was very quickly able to operate the basic functions. The feature that I've found best with this compared to other similar toys (he also has one of the ones that you attach to the pushchair but he's not even half as interested in that one), is that everything the child does with it gives some sort of response, including turning the steering wheel which is what he likes to do best and something which most other toys lack. Turning the steering wheel makes the 3 barrels on top roll which then triggers the toy to inform us that 'C is for caterpillar' or something similar, not that I'm sure my son really cares because as long as it has bright lights (of which this has plenty) and makes a noise (which it does) he's happy!
In addition to the interactive steeting wheel it has a lever to pull or push that makes accelerating, or screeching braking sounds, a horn that shouts 'out of the way' and 3 buttons, one being a radio which plays a couple of lively tunes, another is a police siren that yells 'hey, slow down!' and another informs the child 'I'm out of petrol'.
My son's nearly a year old now and it's still a hit, especially as now he can actually pick it up and throw it on the floor, making yet more noise! Fortunately it's very durable so it just carries on regardless.