http://www.teamfortress.com/scoutupdate/sandman.htm
That's the first weapon release. They're doing updates one a day for five days after this. I think it's three weapons, achievements, a new mode, and a new map.
As for reactions to The Sandman...
Good:
-No doublejump balances everything out
-Stunning will bring in some interesting play elements
-Possible sniper counter!
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Bad:
-Some asshole will MASTER it
-It's REALLY GAY for repelling Ubers, like a long-distance compression blast
-Lucky shots from afar will keep you stunned for a hella long time
-What kind of name is 'the sandman?' Bo-ring