MA
We had three ITV regions at home, London, Southern, and Midlands
The time-shift thing was really handy (particularly pre VCRs)
There were programmes that I would not have seen with just one region
Fireball XL5 (ATV only)
WKPR Cincinatti (ATV/Central only)
Tiswas (early series) ATV only,
The Time Tunnel (Thames only)
Foreign Language movies (Southern only)
Saturday Scene and 'Our Show' (LWT only, later Southern too I think)
Most people under 30 now would be baffled by there being "outrage" over not having two versions of ITV but it genuinely did give you an extra viewing option for significant periods of the day (typically weekday afternoons, late night and weekend afternoons) and in a way provided a +1/catch up service long before they were even thought about thanks to different regions showing the same shows at different times.
We had three ITV regions at home, London, Southern, and Midlands

The time-shift thing was really handy (particularly pre VCRs)
There were programmes that I would not have seen with just one region
Fireball XL5 (ATV only)
WKPR Cincinatti (ATV/Central only)
Tiswas (early series) ATV only,
The Time Tunnel (Thames only)
Foreign Language movies (Southern only)
Saturday Scene and 'Our Show' (LWT only, later Southern too I think)