I bought this set for my 4 year old daughter at Christmas, and, after a few hours, she announced that she wanted to play with it every day and every night. That's quite a recommendation, but not all good news because there's quite a lot of Railtrack type maintenance for the adult involved.
Firstly, to clarify a point made in another couple of reviews, the power is designed to cut out if the engine is derailed, as a safety measure. You have to disconnect the power supply for one minute, but in practice, it is far less than that.
I would also say that issues with the couplings are exaggerated. Yes, one came off, but they do fit back on again. Care has to be taken, obviously, so a little supervision is needed.
The track is quite hard to fit together and you must get it right, with smooth joins, but the main issue for me was the points, which cause derailment in some situations. I worked out that it was dependent on which way round the track the engine pointed, it worked just fine after that, forwards or backwards. But really, they should work better than that.
In a previous role as Santa for my son (now 20, so 17 years ago) I bought a Hornby set and had all the same problems, only I was less patient with it back then and ended up nailing it to a board. That made things even worse. So this is not a recent thing that can be blamed on China, train sets have always been fiddly. But still good fun if you persevere.