Coexistence of different versions of ESXi

I am planning the upgrade of a vSphere 5.0 infrastructure (vCenter 5.0 and ESXi hosts 5.0) to version 5.5 u2.

We will start from the vCenter

For some times (days or weeks) we will have different versions:

• vCenter 5.5 and ESXi nodes 5.0
• vCenter 5.5 and some ESXi nodes 5.0 and other ESXi nodes 5.5

At the end of the process everything will be alligned to version 5.5 u2.

Is there any known issue or anything to consider for the period whith all the ESXi nodes or some ESXi hosts still running 5.0?

Is there anything we won't be able to do or we should do in order to let the whole of thwe infrastructure run without causing problems to users?

Regards

Marius