SoftEther is an amazing piece of software. As mentioned I was a little dubious of it back when it was closed source and touted so many features. After going open source I trialled it on a small network (~40 users) and it was rock solid.
My only gripe was user management. It lacks an LDAP or PAM integration, substituting RADIUS instead. No biggy, I can set up a SoftEther->RADIUS->LDAP bridge. The caveat is that SoftEther will only apply RADIUS authentication to accounts you manually define; so you must create a user in SoftEther and enable RADIUS for them. This may have been fixed by now, but was rather annoying back then!
My only gripe was user management. It lacks an LDAP or PAM integration, substituting RADIUS instead. No biggy, I can set up a SoftEther->RADIUS->LDAP bridge. The caveat is that SoftEther will only apply RADIUS authentication to accounts you manually define; so you must create a user in SoftEther and enable RADIUS for them. This may have been fixed by now, but was rather annoying back then!