I like them too, particularly Mark. Tyler's fine but I'm not sure about Aaron yet. Saying that, I used to think Mark was a very poor actor but he's improved such a lot in the past year or so.
Tyler's my favourite (maybe partly due to his looks...) but I like Mark too (and his looks too!). I think you're right about Aaron - he's probably not as good an actor as Tyler and Mark, but I quite like his character and think it works well to have a middle brother, so I'm hoping he'll improve a bit.
Naomi's a great character, but I prefer her with Paul.
Paul, Susan and Karl are my absolute favourite characters. Neighbours wouldn't be the same without them.
Totally with you about those three. Particularly Paul - perhaps partly because he's the only original left. I think I'd add Toadie in too as an essential character.
I think Naomi's such a good character and actress that she works well with whoever they pair her with (including friendships). I think she's fine with Paul and I don't mind them being together, but my first choice would be her with Brennan.
From the younger cast, my favourites are Imogen and Daniel (which is why I'd like to see them together).