My findings are completely un-scientific, but, in my unbiased and totally correct opinion, it was a big mistake. I hate it. Yup, HATE it! Why, you may ask? Well the main problem is I get muddy colors. The aquas and greens tend to turn a little bit red, the gold pink gets murky- in short it is unreliable, and I really like nice, pure colors- the ones I thought I used, not some random colors the gas decided to give me. I love organic colors, raku frit, reactive glass, silver reactions, but this is a whole different animal. The beads I made using the propane won't be sold online- they're just not nice enough! They will end up being bargains at my table, until I get tired of looking at them and just end up giving them away!
As far as finding propylene, if you are looking, be sure to call all of the welding supply places you can find- the price varies wildly. And one more thing- no matter what gas you decide to use, don't let the tank get too hot- the gas will act erratically if you do. And be sure and drain the line at the end of each beadmaking session unless you want to see a large green flame that doesn't go away when you turn off the torch!
P.S. the fish at the top of this bit of chatter was made on a hothead torch, using propylene gas.