I have been to Uttar Pradesh and Uttarakhand. Though our ticket was reserved from SC till NDLS, we had to travel from New Delhi to Moradabad in unreserved class and it was my worst worst worst experience in Indian Railways, even the loco broke down. We were there for 10 days in those states and had to take trains frequently. It was 2016, I didn't had accessibility to my laptop and neither I had much knowledge regarding the reservation system, I had to stand in the tatkal queue consecutively for 4 days to book ticket from New Delhi to Hyderabad (or Warangal atleast) but I was still unable to get the tickets. We traveled to Agra, and from there took unreserved Kerala SF till Warangal (almost died).
...
more... I swear I will never ever travel to North India (specificly UP, Bihar, UK) again in trains.
I am not biased but my experience in South India (Bangalore, Tirupati, Coimbatore, Ooty) was epic and hassle-free.