ok then.
>> Were you having problems with the cache?
Yes ! We are working with a custom federation provider and we are having problems with users that did not have an email adress when they first logged in. Once these users logged in it is impossible to udpdate their email adress without doing a hard sync from the admin console. We DO NOT need things to work this way as it needs a human action with all the drawbacks (not realtime, week-ends, administrator absent, etc.) and we prefer something more automated.
The only way i see is to disable the cache and force the user information to be updated from the database all the time or .. you could have a better solution probably !