For me personally, I did have to use twice as much as cotton. initially I used just a tad bit more then cotton and after an hour I started to hear that "sizzle after letting go of the fire button sound". soon after dry hits. When I opened it up the wick looked whimpy and had sagged. This rayon doesn't swell like cotton, it actually remains the same size or actually matts some. After increasing the amounts next, it worked great. Tbh I don't think the results would be good in a kayfun if one used the same amount of rayon as cotton.
I agree completely, though I'm not certain that "twice as much" is what I've ended up using; I do know it's considerably more than I used with cotton. When I first put a new wick in, I juice the ends and place them just-so on the little ledges, before screwing on the chimney bottom. As soon as I did this with the rayon, using just about the same amount as I would with cotton, it wicks so well that immediately the entire wick was saturated, and I could clearly see that it was definitely not filling the coil. So I pulled it out and then I did use "twice as much", and that worked great for the rest of the day -- but the next morning, I started getting that infamous burnt taste, and when I checked it, I could see that although it wasn't as black as cotton would have gotten, it was definitely scorched. So I did a new one, still using a good bit, but maybe only about 1.5 times as much, or just a bit more, but not twice as much. That was Saturday morning, and this particular coil/wick is still in use, and still vaping very well.
I don't think I notice any "difference" in taste, but maybe a bit stronger, clearer taste of the e-juice. The main benefit I can see is that with cotton, I could not go above 8.5w without IMMEDIATELY getting a burnt taste; with rayon, I can go to 9w or 9.5w, and get no burnt taste, but obviously, a lot more vapor. I didn't notice any particular taste of "breaking in" just from the rayon, but with the one I've done that I also replaced the coil along with the wick, I did notice a short period of a *slightly* odd taste, probably just the brand new coil breaking in. After about 8-10 hits, that was gone, and all I could taste was a VERY clear taste of the e-juice.
Game changer? Maybe not. Better than cotton, and easier to deal with, when you've had issues with a burnt taste from cotton? DEFINITELY!
Andria