Just watched it on catch up. It's a bit odd.
It's quite strange to expect spotters to send in photos "live". Whilst BBC4 is available on mobile devices, I expect the vast majority of people will have been watching from home, and that most spotters out and about would not have been watching the show.
This kind of show has the inherent problem that us rail enthusiasts may think it too superficial, yet the "normals" would see it as little more than an odd curiosity. Watching Dick Strawberry frothing over a 66 would probably only serve to make us enthusiasts look even weirder to the wider community. As such, it risks not pleasing many people.
I did quite enjoy it though. Some of it was dull, some of it quite interesting. I'm not convinced that trainspotting alone has been the best approach - I think looking at the operations of the railway as a whole would be of much greater interest, both to enthusiasts like us and indeed to the general public. Certainly there'd be room for spotting, but like some previous commentators I would have preferred the show to look at the railways as a whole.
Dr Fry is a brilliant presenter, but I'm not fully convinced that she wanted to be there! The maths is a random addition to the show (although the segment on GMT was worthwhile IMO), and frankly it's not even interesting mathematics. I'd much rather see her doing programs focussed on mathematics - if someone from the BBC is reading, can this become a thing please?