We are running 2 separate md3000i's with Dell R710's. I have ran it on vsphere 5.0, 5.1, and 5.5.
The current 5.5 host runs Veeam DR, so it has I/O from Veeam jobs but only hosts 2 running vm's.
We are moving 2 production hosts to 5.5 soon, not anticipating any problems.
Make sure to have the newest firmware on the md3000i itself - the last firmware update I am fairly sure is very important for compatibility above 4.5.
The few rumors I've heard about compatibility were about failover - I still need to test failover by pulling network cables and forcing a failover to make sure vmware doesn't freak out.