The Data ONTAP PowerShell Toolkit certainly does work with Data ONTAP 8 (except cluster mode). There are a few API groups that have not yet been propagated from 7.3.x to the 8.0 releases, such as those for working with CIFS ACLs and network configuration. But the vast majority of the Toolkit should be fine with 8.0.x (7-mode).
Hello, Tim. Please understand that I can't make any commitments in this regard, but I'm told that Data ONTAP 8.0.2 should have the missing APIs for network configuration and CIFS share ACLs. That release is still some months away at this point. I think it is also a fair assumption that Data ONTAP 8.1 will have these APIs in its initial release.