I should have said in comparison to something like say ocean forest, it just doesn't stand up. Yes its much better than miracle grow soil, or super soil, etc. But the fact is, out of the bag, it holds too much water, lots of compaction, there is massive pH flucuations, etc.
Outdoors, used as a "buffer" soil in the ground, I'm sure it would work just fine. But in a temp controlled, indoor environment, it just isn't nearly as quality of a soil as ocean forest. The couple of dollars you save on a bag of happy frog, you end up spending on perlite. Without it, you risk overwatering, and compacting your grow medium.
This has been my experience with happy frog, and on the other board I am a member of, many members have problems with it as well. If it works for you, keep on using it. I wouldn't try and fix something that isn't broken. But for most of the people I have spoke with, they would prefer ocean forest any day of the week.