Thanks for the comment
Yeah, I'm aware of the challenges, but testing has proved pretty stable, and hasn't really bitten me too badly so far. The plus side is access to much newer versions of packages, with better functionality.
I found the answer eventually, so incase anyone else has the problem, it was phpldapadmin specific, and related to the new config.php file format introduced by 0.9.7 - it needs the login attribute set to "dn".
Thanks for pointing out the bug reporting stuff, I will make use of that in future!