The position of the $each modifier in an update used to be significant in 2.4, but it no longer is in 2.5/2.6. This has been discussed in HELP-254, SUPPORT-708, and SERVER-10009, and should be updated in the 2.6 docs.

This is mentioned on the doc pages for the $slice and $sort modifiers, although not on the page for $each itself.

http://docs.mongodb.org/manual/reference/operator/slice/#op._S_slice
http://docs.mongodb.org/manual/reference/operator/sort/#op._S_sort