I have stayed at the Fairmont Makati several times. As per FPC T&C's they do not accept the Suite upgrade vouchers. However I have been successful in using them there a few times. I send them a request in advance, they reply it will be dependent on availability upon check-in and more than half the time I got upgraded to the corner Suite.

The do accept room upgrade certs. This property has two categories of 'standard' rooms: the Fairmont rooms and the slightly more expensive Deluxe rooms. They are the same size and layout, Deluxe is just supposedly better location (corner, pool view etc).

The trick is to book a Deluxe room and then request to use the room upgrade cert. This way they will upgrade you Fairmont Gold room with lounge access. The lounge is indeed very nice although breakfast offering there is limited. If you're in a Gold room you do not get a complimentary breakfast in the main restaurant, only in the lounge.