I had been wondering why MicroScalextric sets used to retail around the £75 mark but are now nearer £40. This set answered my question. Although my four year old will more than happily play with it, I can see it for what it is, which is badly made, badly designed, cheap and really quite nasty.
The first problem is the track. It is fiddly, flimsy, doesn't lock together well and Hornby are clearly so disinterested that they don't even bother to suggest where you should put the crude track supports when you need a flyover for one of their suggested track layouts, and indeed it is quite easy to push the supports clean through the track. The 'crash barriers' are particularly cheap and nasty, don't clip to the track well and they certainly don't keep cars on the track. If they are trying to market this set as something of an introduction to slot car racing, as I think they are, they really need to make the track a lot tougher.
The hand controllers would be OK but they have a tendency to stick very slightly on so you can let go completely and the cars don't stop.
The cars are pretty crudely modelled but at the same time well enough, and given they fly off the track with monotonous regularity they could perhaps be made more robust. The body comes off all too easily. After about an hour of use the pick-up braids are already looking like they have had a hard life, one rear wing has come lose, and my four year old seeing that snapped off the other to match with no effort whatsoever.
The biggest problem is the speed and roadholding of the cars. Basically they can go so fast they are just a blur and in fact they probably go about five times faster than they really need to. The road holding is really quite impressive, too impressive in fact. If you operate the cars at about 95% of maximum the cars flash around the track and don't fall off. If you go flat out they go flying off. That is the only skill involved.
So if you want to keep a small child amused for a while at a reasonable price, this might be a good choice. If you are looking for a good introduction to slot car racing in a small space, I don't think this does the job. If you are hoping for a smaller scale quality slot car racing experience, forget it.
Update:
After approximately four uses, both cars now have completely broken rear wings that are beyond fixing with adhesive so I'd certainly advise choosing a set with rather more robust cars in it for younger children. One has had its pick-ups ripped out all too easily. If a car stops near any joint in the track it has to be moved to be restarted. Track sections are already showing weaknesses around the joints, and in particular leaning even gently on the raised sections of track really isn't to be recommended at all. I've downgraded my overall rating for the product.
My son seems unperturbed by all the problems, it is me who is disappointed and deeply unimpressed.
By the way, although the instructions still refer to this set as 12V, mine came with a 19V mains adapter and a 19V sticker on the outside.