Is there any great benefit from a brace, post acl reconstruction to ski?

Depends: It really depends how far out you are from your surgery. There is really no good data that shows that bracing impacts recurrent acl tears. If however you still feel weak or inhibited a brace is not necessarily a bad thing but if you have any reservations at all i would not advise skiing w or w/o a brace as a brace won't prevent another tear.