I am also having this issue on 5.5 (not u1) latest build version of ESXi 5.5.0 build 1746018. As an example, we have a thin provisioned VM that is allocated 550GB, actual usage when looking through Storage Views shows the correct usage of about 500GB. The summary page of the virtual machine shows 88.93GB Used Storage, Not Shared shows the same value, Provisioned showing 550GB. We are currently using EMC storage which is supported by 5.5, and the drivers / firmware / flexcode are all on a supported level.
I'm currently getting VMware to investigate this issue, and I'll let you know what they come back with.