We left our datastores on vmfs3 after our migration, but now that we are a few weeks after it, we are using storage vmotion to move VMs onto new storage groups with new datastores. Once we move them all, then we will reclaim our old datastores and probably carve them differently. again, doing all of this during the day; no maintenance window required.
good luck with vconnect. we have been burned by it's buginess in the past, and learned that HP no longer has anyone that can answer the tough questions about it (they actually told us this!). All I can suggest is make sure your firmware is up-to-date before you put production servers on there.