I successfully upgraded a Kingfisher flight from HYD > DEL today that leaves tomorrow. I had tried last week with no success, it had said my flight was not upgradable "at this time" so I tried again on a whim.

-According to the TOS, the upgrade is seat only, i.e. no extra miles, baggage allowance, etc.
-I initially chose optiontown's India site as I am in India, but then it would not accept my US-issued credit card. I redid it on the US site with no problem.
-The upgrade cost $57 USD.
-Time between request and confirmation of upgrade was 4 1/2 hours; I cleared about 27 hours before the flight.