Can confirm it also works for Tinantia pringlei and both Pilea insolens and Pilea matsudae.

I worked in a mycorrhiza research lab for a year so I know a little but it is a very complex area of research with lots of conflicting data. Generally I would say completely sterilising soil would be a bad thing (and pretty impossible, fungi are tough things, you are unlikely to kill everything), not only do you kill off anything beneficial that might be in there but you also ruin the soil structure and potentially create toxins from the breakdown of compounds in the soil during the heating of the soil. The only way to avoid these side effects would be irradiating the soil which I'm guessing most of us don't have the facility to do. Only reason I could see for doing it would be to kill off weed seeds. A good place to start to learn about all things fungal is "Entangled Life" by Merlin Sheldrake, there's a good section on Mycorrhizas in there amongst other things.

Rooting hormones are Auxins (a group of plant hormones that control many different things in plants including plant growth habit, leaf shape and the formation of lateral branches), I personally never use them but one of the things they do do is encourage the formation of roots. They are produced in the growing tips of plants and travel down the stem towards the roots (or where the roots will form on your cutting) so I always leave the growing tip in my cutting until I am sure it has roots. The willow thing is probably just the build up of the auxins produced by the willow being excreted into the water by the cuttings, can't think of a scientific explanation for the honey but it's interesting to hear about, I might have to give it a go.

I propagate lots of plants this way, very handy for things with larger leaves. I find everything that I have tried with a square stem roots easily this way. Particularly effective for larger leaved Salvias such as "Amistad" (not so good for microphylla types), Coleus and Plectranthus work a treat, works really well for Impatiens and currently I'm trying Pileas, so far seems to be working. Anyone know anything else it's particularly good for?