Took me less than a morning to fit it all. I haven't fitted the outside siren yet but all the wiring to keep i on charge is in place so It will take perhaps an hour when I get round to drilling a hole through the outside wall!
So no problem but I only give 5* where the performance or service is well above what should be expected. So 4* is very good (probably equivalent to most people's 5*), for me 5* would need to be exceptional in some way.