I'm on episode 10 of series 5. I only reached season 5 on Wednesday.
I'd never found this series especially binge-able, but season 5 has really changed that. Before I used to think it was good if I'd even got through one episode, and most of seasons 1-4 I'd watched with my brother (who's always found it binge worthy).
I think it's the fact I'm meant to be revising that I'm finding it so good. When you consider studying Macroeconomic policies, or watching a TV show about female prisoners running a prison, which would you rather do? I think the answer's pretty clear to me.
I think what I like the most about OITNB is the flashbacks. The episode I'm currently on has Piscatella's, and it's very insightful into how he's such a horrible person.
One thing I think you need to remember with this show, however, is how they seem to low-key glorify prison. As someone just finishing education, I can almost place myself in the situation by comparing it to my secondary school, but then I remember that there is indeed a difference between the criminals in Litchfield and students at my state comprehensive. That being said, I feel like the backstories are good and help normalise the situation.
I also like how they include the guard's backstories too - I especially liked Bayley's. I also feel quite sorry for the guards too this season - they're being put through a lot.
Either way, it's a very good update to a very good series, that in my opinion helped define Netflix into the cult staple it's become today.