I've heard a number of vibraphonists comment that there's no way to eliminate rattles from the instrument. I've owned a number of vibes and the rattles have always been present. My vintage Musser M55 was rebuilt by the master vibraphone maker Gilberto Serna before his passing (Century Mallet - Home Page).
I have a recording session coming up and I'm interested in other people's experience. Is the Omega vibe the most rattle-free instrument? Or maybe it's a function of age - my M55 is quite old and I while have no cases for it, I'm very meticulous about wrapping it for transport.