Here's a picture of my Spiral scarf. I'm using Koigu and Claudia Handpainted for alternate hexagons, since the colours seem to complement each other well, and the gauge is really loose and drapey, on size 5 needles. It makes for a softer scarf this way, I think. As you can see, I didn't knit it all in one direction. I started with a couple mid-sized ones, then knit two larger ones and joined them with a fifth one. My largest is at 20 stitches so far, and I don't think I'll make a larger one than that.
This is a quick, fun and addictive knit! Incidentally, the cast on question I had a few days ago was resolved easily. Basically, no matter what cast on you do, just make sure you leave a tail long enough to pick up half the number of stitches of a side. That makes for a stronger join with the next hexagon. As for the very first one, the tail doesn't matter. I like the nice, pointed edge of the long-tail cast on.