Off the top of my head:
Great interaction between characters and characters aren't so restricted to the immediate people in their storylines, they mix now. And as others have said great characterisation period.
Billy having a responsible job and actually being taken seriously for once. Phil actually showing Billy respect the other day. I really don't him to be regressed to loser again.
Billy and Jay working together at the funeral directors, I always thought that Jay should have been with Billy not Phil.
Phil stopping grunting, sighing and playing silent/walking off and actually talking about how he feels - OK it's only a bit but it's a start!
Sharon calling Angie 'Mum'. Drove me mad under DTC when she referred to them and Den and Angie.
The Lee and Whitney storyline but I'm not going to lie, I'm getting a bit impatient with Lee now even though I know he's depressed and has low self-esteem. However sometimes he's frustrating to watch especially when he's saying to Whitney that she's going to have the best December EVER even though (for once) she hasn't even harped on about wanting the best Christmas ever that I recall! Gaaaah! But I suppose it's realistic.
A Kathy I recognise being back not the mouse who returned.
Martin and Stacey

.
That's all I can think of for the moment