What do you mean by wobbles? Do you mean radial play or axial play? Every Canon body I've owned has had some radial play (rotational at the mount) in varying amounts.
I think a lot of those that say they have tight lenses would be surprised to discover this same play if the lens was held tightly in the tripod and they moved the body. The reason most never feel this play is that when the body is mounted in a tripod the lens is never moved. There is no reason to place the force required to feel this play in normal use.
The whole game changes when you mount the body to a rigidly tripod mounted lens. You grab the body to change the framing and that's when you'll feel the play there. It's slight, but on every lens/body I've owed from Canon there is play there. I just grabbed my 24-105 mounted on a nearly new 7D (with a metal body) at the base below the focus ring and then twisted, sure enough, slight play. When you mount a short lens (in other words, you mount the lens to the body) after you mount it there is no rotational force placed there. The body controls the whole shebang, you never feel the movement, but mount a long lens on a tripod and mount the body to it...
The 60D/Rebel series are not the first composite camera bodies that Canon has used. The EOS 3, a highly regarded, semi pro body; way more body than a 5D or 5D II, was a composite body. It is sturdy and tough as any body. The EOS 3 is a great camera body, with an incredible eye controlled, 45 point auto focus system. This system premiered in the EOS 3 and was subsequently placed in the EOS 1V and 1D bodies (though without the eye controlled focus which proved to be somewhat problematic).
So what I am saying is don't listen to the whining about the "plastic" body on the 60D. It's just that, people are upset that somehow their XXD camera bodies are devalued by Canon's choices on the 60D. The XXD upgrade path is now to the XD camera bodies. The name the body is called means nothing. Buy a camera, use it to take great photographs, display the great photos, if they are great, and inspire, does anyone really care what body they were taken with?
Rule books are paper they will not cushion a sudden meeting of stone and metal -ekg-