nslcd/nss-pam-ldapd has its own share of problems. I would say that calling SSSD unproven is unjustified. It exists for quite some time, is actively developed and solves many problems that are still present - partly per design - with nslcd/nss-pam-ldapd. Finally, configuration with SSSD is much easier and much less error prone than the old nslcd/nss-pam-ldapd-combo.
nslcd/nss-pam-ldapd has its own share of problems. I would say that calling SSSD unproven is unjustified. It exists for quite some time, is actively developed and solves many problems that are still present - partly per design - with nslcd/nss- pam-ldapd. Finally, configuration with SSSD is much easier and much less error prone than the old nslcd/nss- pam-ldapd- combo.