The antenna or called RFID tag is good in free space. But if you attach it to the metal or conductive surface, it won't work. There are some RFID tags which are specially designed for metal surface.
Hi ceg,
From what I've seen about chip antennas, the gain is less because of the size but from the plots given in digi-key for some chip antennas, they seem to be reliable and meeting specs. Gain is obviously not great but with the size reduction, I'd think it'd be cool to try using them.