I had. Unfortunately I have not done any lab tests on LH and FSH to prove it works, but I can tell you taking it during cycle prevented testicles from shrinking and kept sperm quality (that one I checked).
Even if it is not a silver bullet for HTPA shutdown I think it is quite beneficial to have it. It can only help in that regards and not only that. The increased work intensity of incycle training really beats up immune system and may people get sick in that time. LDN is proven to boost and modify immunity.