I say take the plunge and go for it if you have some good network guys to back you up. They must be willing to learn a few new tricks, but it's the same nexus code they're used to. Make sure the 1000v is fullly licensed too before going live because bad things happen when it's not. The recommendation is to trunk up a dedicated host for your intitial test so you have the most versatility in choosing your design. Ideally you should have 2 hosts to kick around to test vMotion, HA, etc. If you can't get a dedicated test bed, migrating live workloads is fine (once some test VMs are working of course).
Keep in mind you can mix and match vss, vds, and 3rd party vds such as the 1000v till your heart's content and it's fully supported. Additionally, the migration from vss or vds to 1000v is gui driven (from the CTRL+SHIFT+NETWORKING page). To install the VEM on the ESXi hosts you can use VUM, vCLI or inject it into your ISO at build time like any other VIB.
One option you may choose is to move only the guest traffic to the 1000v so you can take advantage of enhanced sniffing capabilities for example, without making any changes to your current mgmt, vMotion, etc. However, if you were going all in (i.e. migrate everything), you would probably want to bundle more NICs together and dotq trunk (guessing you're just using access ports now). Regarding your iSCSI I cannot comment so you should look into any gothchas or best practices.
On to the topic of packet, control and mgmt vlans for the 1000v - those can all be the same VLAN if you want. However, most people create a VLAN for each and trunk as needed. In your case you can use the same mgmt vlan for the 1000v that your ESXi hosts use (that's how I typically do it). Next, create 2 new VLANs for the packet and control.
Note: Consult the latest Cisco documentation for the new best practices regarding routed vs non-routed choices for the 1000v VLANs. Also an advanced topic that is worth noting is the strongly recommended MAC pinning instead of subgroup CDP.
As a final note, the Cisco 1000v support engineers are freaking amazing so if you ever get in trouble they will webex in and save your day.