I really do love them. They make sock knitting so much easier for me. If you try them I say start with a fairly basic sock, just to get used to them. The small size made casting on a bit awkward at first, but now I have no problem with it. I did have to learn to hold them with just a couple of fingers as opposed to my whole hand as well. But after an hour or so of playing with them, it was no problem either. For me if I cast on less than 66 stitches or so, the first few rounds seem a bit difficult, but after a few rounds of ribbing, once again, no problems.
When you get to the heel, what I do is knit the heel flap and turn the heel on DPNs, then pick up the gusset stitches with DPNs, all the while leaving the rest of the stitches on the circ. I will knit the next round after the stitches are picked up all back on to another circ. If you only have 1 circ. then you can transfer the other stitches onto a DPN as well and then knit them back onto the 9". I'll just use stitch markers to help me remember where to decrease. I can knit the whole sock except the heel flap and turn and the very end of the toe with the 9".
Hope that helps! Good luck with them!