I'm checking on this for you--someone will get back to you with an answer.
ESX API should be working also with older versions of ESX, although there might be some pieces of information missing (not supported).
As an example, we have successfully connected via API to ESX 2.0.
Do you have some older version of ESX that is not working for you with the new API polling?
thanks and yes, it is ESX 3.0.0