We run separate on the standard switch, but don't on the distributed switch.
Standard Switch - Need from 4 to 6 NICs
Switch 0 - MGMT and vMotion (pin MGMT active on one nic, and vMotion on the other)
Switch 1 - Guest Networking
Switch 2 - Storage Networking (if needed, mostly FC or FCoE)
On the distributed switch we run converged networking with Multi Adapter vMotion, and just use NIOC to tag traffic with a COS value and prioritize traffic leaving the NIC. All four NICs on the distributed switch are active for all traffic types, except for vMotion where each NIC has a specific vmotion vmkernel interface pinned to it.
The more common way to run the VDS is to use the active/standby/inactive settings for each port group to separate your traffic across the physical NICs connected to your VDS. You could run a standard switch just for management, but we haven't really felt the need to since the introduction of the rollback feature of 5.1.