One disadvantage of 3.5.x-Codes is, that you need 256MB RAM on a 8690SF and 128MB RAM on a 8691SF-Module (Required in Release Notes). If you use the 3.5.x-Code with only 64MB RAM it may work fine (it depends how many features do you use eg. Multicast-Routing), but you loose your Nortel-Support.
3.2.0.0: After Link-loss we lost Policy-Based VLANs
3.3.0.0: Doesn't support Policy-Based VLAN with SNA-DSAP-Type NOT 04, but works stable in our Enviroment.
3.5.0.0: No specific problems detected.