I did a swatch, I did the maths, and now I've started the Crocus jumper.
I've used several sources as a guide for my pattern - '1000 Sweaters' - which gives a good idea of the structure of a jumper, and ideas for necklines, etc; and a couple of home-made jumpers to use as examples.
The wool knits up nicely, although it feels a little strange using 4mm needles after all those chunky hats.
I switched to circs after doing the ribbing. I also didn't use a smaller size needle for the ribbing - I didn't want the gathering effect that this would give. I'm just about ready to start my first stripe of Opal.