I just had a chat with several people of VMware about the fact that the RCLI is read/write as of ESX 3.5 Update 3. As it turns out, these new APIs were opened up unintentionally. This unintentional change happened when VMware was resolving an API-related bug.
My VMware contacts tell me that this bug will be fixed shortly. So, do not get used to them because they will become restricted again. This only applies to customers who downloaded the free version of ESXi. VirtualCenter and VI (Foundation, Standard, Enterprise) customers are not affected.