Toby's Estate in Woolloomooloo and Campos do it for me.
Toby's has a wonderful decor - suited to coffee dates, business meetings, breakfast with friends... it has a very nice, funky vibe about it. Most importantly it feels very relaxed - leaving you to have your coffee in peace.
I have been here for training on several occasions and for coffee on several others - the coffee is consistently fantastic (including my girlfriend's soy decaf, perhaps finer than most full-cream regular coffees I've had in Sydney). There is a lot of passion behind the people at Toby's, and they have a very friendly vibe (except for that one Barista.. you can't miss him..).
Toby's is 129 Cathedral Street, a ten minute walk from St. James station or Kings' Cross. I haven't been to the Chippendale cafe (opposite Broadway), but I've heard it isn't as good as this main branch.
Campos, on the other side of the CBD, doesn't have the same vibe of relaxed, easy drinking - it has more of a frenetic, obsessive-compulsive buzz to it. The coffee here is taken more seriously than food at most fine-dining restaurants (indeed, it was ranked above Tetsuya's at one point on eatability). As a Barista, this is an attitude I greatly admire and so I have nothing but respect for Campos by default.
The Baristas have a no-talk policy (I think) here but that's irrelevant, I find that when I am in Newtown, I am often on my way somewhere. I normally order take-away, but sometimes I sit down at the bar to slam down a coffee. Either way, I'm out within minutes with a very pleasant aftertaste guiding my back down King Street.
Campos is about a 15 minute walk from Newtown station, on Missenden Rd. just off King street.
... hello, by the way C: