Here's what I think:
Best
-Damian Lau
-Roger Kwok (so funny as Ah Wong)
-Charmaine Sheh (I used to think she sounded annoying, but she's really improved!)
Worst
-Sammul Chan (very cute, but could work on his crying skills)
-Linda Chung (although she wasn't that bad in Heart of Greed, I still think she needs some practice)
-Myolie Wu (I just don't like her)
When I think of some more, I'll add to the list.