In Monitor, we provide ability to access VM console directly from our application (one of the tabs available on VM view essentially). This no longer works with unlicensed ESX 3.5 Update 4. So in order to do this now, you need to open VMware Infrastructure Client and do it in the same way you are doing this today to connect to a VM running on your free ESXi. So it is just a matter of using extra application, not a big deal - just a little convenience that is no longer available for unlicensed hosts. But actual monitoring functionality is not affected for unlicensed hosts - everything else still works.
We plan to release 4.0 in a few weeks.