I haven't played with DSM3.0 so I can't answer that part, but the NetApp ESX Host Utilities analyzes the target WWPNs and figures out preferred paths to avoid using proxy paths.
I haven't used the Netapp ESX Host utilities, but we are using a script that looks at the paths available for each lun and alternates it between the paths on the primary head. (nothing like testing the script to discover a logic error will generate a lot of ASUP's)
What is included in the NetApp ESX host utilities that you find useful?