e-wax is an emulsifier, and the purpose here is to get your oils to disperse in the bath water. i did get around to using the e-wax as a test, and while it worked fine, it was more difficult to use (the higher melt point meant that i spent more time worrying about the temp of my oils).
i've recently gone back to polysorbate 80, and i've decided that i like the foaming action and i'm just going to go with it. i think i get slightly harder bombs with it, and since most of my sales are online i want a bomb that will hold up well to shipping.
it's possible to make bath bombs with no emulsifier or solubizer at all, but if you do and you use heavy oils, you might get an oil slick in the tub. if you use light oils only, the bombs may be a bit soft and crumbly. it takes a little tinkering to get rock hard bombs that behave exactly the way you want them to. they're fun to play with, though.