Not only entertaining but educational as well. To make it possible to build the machines, the teams must be able to grasp the basic operational principles behind each one. The explanations they give are a great way of passing that understanding on to the audience.
For some of the projects, I suspect that the scrapheap is "seeded" with some specialist items without which successful construction would be virtually impossible. However, that does not detract from the flow of the programme at all.
The producers also like to select teams full of colourful and eccentric characters. When people with nicknames like "Bowser", "Nosher" and "Lurch" feature, you just know they aren't going to "go quietly into the good night".
I rate this show very highly. I think any country whose citizens pride themselves on their ingenuity and "can-do" attitude would get a real kick out of this programme.
Channel 4 should be very proud of their work.