So far, these have worked well. I did need to use a dryer sheet on one load of sweaters on a very dry day due to static. Otherwise, they have worked great and left clothes and stuffed animals soft with no chemical smell.
I've used these with lighter fabric clothing and heavy fabric towels. Drying time seemed to be less, no static with sweaters, and all fabrics were noticeably much softer than with dryer sheets (I did just start using vinegar as a fabric softener in the wash so I'm not sure if it was that, the wool balls, or the combination). I've used plastic dryer balls before (so ashamed!) and never really noticed the difference I did using these. And since these balls are smooth but firm, they didn't damage delicate fabrics. After a half dozen dryer loads or more they look like new and I just leave them in the dryer ready for the next load. Love them and would absolutely recommend along with the exceptional and very personalized customer service provided by Rachel!