How to integrate properly Kerberos based SSO in Drupal 7
After some researches and tests, I finally made a choice.

In most cases, I'd prefer use native or add on features. This provide better integreation with the product (here Drupal) and it's more a Logic solution than a technical one (which is quite easier).
The LDAP_SSO module allow this kind of configuration.

Nevertheless, I was not able to configure it this time, mainly due to poor debug facilities. Even with watchdog, I am not able to know what is the matter. Moreover, my customer have clear procedure to install and use Kerberos, with Apache HTTP and mod_auth_kerb.
Hopefully, LDAP_SSO module allow this too.

After some tries, I will get back here to share with you more advanced comments, but at this time, we clearly go to apache+mod_auth_kerb+fowarded REMOTE_USER.

Edit a few monthes later :

That works great with Mod auth kerb on apache server and ldap module v1.0-beta12 on drupal. 
Even if v2.0 is available, we were facing some issues because some fields were empty and this were causing troubleshootings.
But nevermind, we are able to authenticate et identify users, collect groups and map them to  drupal profiles etc.