I can only offer my personal opinion here and I don't think it should be taken with too much weight because there are so many confounding factors.
I'll explain - typically your average meathead doesnt use any training, healing or fat loss modality in a way that allows any one particular part of the program to be analyzed in a meaningful scientific way. IOW much like the reasoning behind why we tell cycling noobs to start with a simple Test cycle, 'if you have too many drugs in the cycle you won't be able to tell what is doing what'.
For healing - each injury is different for many reasons to begin with. Hard to compare a finicky inflamed rotator cuff with a torn ACL. If you use GH (dosage and dosing protocol/timing being another variable) but also maybe include physio, chiro, masssage, icing, heating, NSAIDS, supplements like curcumin, etc etc. Hard to say what is doing what so it's hard to know what anyone's anecdotes are worth.
Now that that is out of the way, yeah I think they work. A bunch of people I know irl that have used them think so too, and there sure are a ton of people on line who do too (plenty naysayers as well of course).
How well? How cost effective? Compared to GH? Way too hard for me, or anyone else imo, to quantify with any precision.
For fatloss ? Pretty much the same answer of course but I will say that I would be more inclined to spend the money on them for this purpose than for injury, more of an effect is perceived on my part.
Bottom line I use them periodically for both those reasons and I am not one to throw cash around haphazardly.