So do I have to configure  "ip router ospf 100 area 0.0.0.0" on each SVI's on the standby HSRP ? Or is there another way  of advertising OSPF from each nexus rather than configuring it on the SVI's. I got   8 SVI's configured on both Nexus. Or shall I create different areas now for each SVI's ?. Was using a HP L3 switch before doing this core routing role and I assign all SVI's only one area i.e the backbone area.

Anyway help will be really appreciated

You just need to assign all your 8 SVIs to one area.  And yes you need "ip router ospf 100 area 0.0.0.0"  on both active and stand-by HSRP for all 8 SVIs.

HTH

I notice when I do that I cannot  reach some of my VM's hosted on our ESXi hosts that are connected via both Nexus. And other routers in the backbone area seems to see a single subnet from both Nexus. I know I must be missing something I believe

Looking at your topology, you are missing a layer-3 link between the 2 Nexus switches.

Also, is there a reason your Portchannel ids are different between the 3750 and the 2 Nexus switches. (P2 on Nexus and p4 on the 3750)?

They should work fine but its easier if your ids are the same.

http://www.cisco.com/c/dam/en/us/td/docs/switches/datacenter/sw/design/vpc_design/vpc_best_practices_design_guide.pdf

HTH

I think the port channel ID's doesn't matter ? The reason being I have 3 port channel also configured on the 3750 connecting to other equipment's. So I use the 4th port-channel for the inter-switch link between the 3750 and the two Nexus. Can you enlighten me on that L3 link between the 2 Nexus ? I've got OSPF and they can see each other via OSPF with state ad FULL/DROTHER

With my standby seeing the primary as FULL/DR 

Any helpers out there ?