I've just started watching series 5 and I don't find any of the couples as interesting as the ones in previous series but maybe this will change as I get further along. I mainly watch because I love Orna, she's so patient.
I think Jason and Marjorie would be fine if they listened to one another, the autistic bloke is incapable of having a healthy relationship with anyone, including himself, the lesbian couple are probably incompatible as one of them seems to want to shag around (but calls it "evolving") and Chris is a dick. Cuddle therapy my arse.
I remember the throuple from the previous series. I was a bit surprised Orna took them on. There was also a couple that were completely incompatible, Boris and Jessica I think.
Does anyone remember Peng and Will(?I think) from series 3? I felt as though I had PTSD after watching them.