I like the range of eras covered by the programme. And it often draws our attention to records we haven't considered, outside the usual census / parish records... such as school records, military, hospital records.
I'd like it if the research involved was shown in greater detail, though. Often we see a celebrity type a name into ancestry, and magically they find their ancestor in the census! We all know it's not that simple! I imagine a large number of viewers will have an interest in genealogy, and are given a misleading version...