We bought one and rapidly had to buy a second because the cats were squabbling over it.
The one we bought was self-assembly and, although it was simple, it was a tight fit. The metal frame comes in three parts with plastic tubes you have to use to hold it together. Once assembled, you slide the entire thing into the fur cover, which provides it with extra reinforcement. Then you hook it over a radiator and wait for the cats to discover it.
In use, the radiator beds are surprisingly strong and will take the weight of our largest cat at 7.5kg, who sleeps in it while spilling over the sides. It has also supported him and another cat while they 'debated' who got to sleep in it.
They are also hardwearing: after two years, we haven't had to replace them, or the covering. The only sign of wear is a slight drop on the plastic joins in the bed our largest cat uses regularly. The covers are washable, essential for any cat bed, but a light vacuum (or brushing with a hand) will remove most of the fur that builds up. You can also buy new covers if necessary, which extends the bed's life further.
One thing to remember is to make sure your radiator is securely fastened to the wall, as the radiator brackets will be taking the weight of the bed and the cat(s) on it. Also, you don't have to put this on a radiator as it can hook equally well over any level item that can support it,e.g. the end of a bed, although the cats may object to the lack of heat. Also, it is fairly large, and has a metal frame so don't put it somewhere you will walk into it.
Overall the cats loved this one and spend a lot of their time curled up watching the world go by. I like this one because it is hardwearing, easy to use and keeps the cats happy.
All cats love it warm! The Radiator Bed Yumi is adored by all cats designed for all common radiators