the term grey set means no local warranty (not grey color), at the most it is Shop warranty, if the shop has a good rep and you test out the lens carefully, then its worth it
and yes, at $890 it is a good buy. make sure it is what it is first. (ie: 100mm MACRO USM.. if it omits the usm, then its the older version, still good, but should cost much less)
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