Note that the most current version is Service Pack 4. Information can be found here.
Avaya has released Service Pack 1 for IP Office Release 11 firmware. Aside from the usual bug fixes, there are two changes to note:
There are firmware updates to the DECT Basestations - both versions 1 and 2.
The significant change is the support of the J139 phone and that the J169 and J179 phones need to be converted to SIP firmware instead of H.323 firmware. The upgrade can be completed automatically when the phone system firmware is updated.
Depending on the current version of your IP Office, an upgrade may have to be completed in 2 steps.