They've worked out alright for me overall. But, last time I cloned I did some in Oasis and some in rockwool, and didn't see any difference in success rate. So, I'm thinking the extra expense isn't really justified. My success rate seems to usually be in the 75% to 90% range, though sometimes it goes as low as 50%. I'm not sure what causes the differences, but I suspect it's more about when I cut, what the temperatures are, etc... rather than what medium I use.