These are a few questions from a university in Washington state looking to move faculty, staff and students to Office 365:

Can I have an AD domain of university.local  and use Federated ID (Single Sign On) with Office 365?

Yes, provided you leverage an Internet routable domain for your UPN suffix.  For example university.local is the domain the default UPN suffix would be @university.local  this would have to be changed to something like @university.edu in order to leverage Federated ID.

Can I have mailboxes on prem with voicemail in the cloud?

No, you cannot have mailboxes on prem and leverage a separate voice mailbox in the cloud.  You can have a hybrid voicemail approach such as mailboxes that are UM enabled on prem coexisting with Exchange Online mailboxes which are also UM enabled.

Can DirSync provide password sync capabilities with the MS Online ID?

No, it cannot natively sync on prem AD passwords to the MS Online ID. There is a 3rd party tool from MessageOps that can sync AD passwords to your MS Online ID. See it here.

Can I filter Dirsync so I don’t sync over everything?

Yes, however it is not fully supported as of yet since we don’t have protection against accidental filtering of objects. You can filter by OU, Domain, or custom attribute. There are plans to fully support this coming very soon.

Can I have multiple UPNs supported in a single ADFS instance?

Yes, prior to a new Rollup 1 update for ADFS 2.0 it was required to have a unique ADFS infrastructure for EACH UPN required. This Rollup 1 update allows for multi-UPN configurations per ADFS instance.  Grab it here.