Also, if you put the money aside you can just go buy a new one when the old one dies, rather than have the hassle of going through the insurance company who will send someone out to assess the machine and then spend weeks debating about fixing or replacing!
It's a con. I cancelled my insurances and had the sales rep on the phone basically telling me I was an idiot as "anything" could happen to my appliance! I've never had any problems and if I do, I'll either get an engineer to look (OK, probably look myself or get Mr P on the case), or go and buy a new one.
Save your cash, by the time the manufacturers warranty has expired you would be able to replace it anyway.