Looking though a comparison of the dota_english.txt file, this string strikes out to me, in a big batch of error messages
"GameUI_Disconnect_NoMoreSplits No more split screen slots"
Also, passwords for replays and spectators:
GameUI_Disconnect_BadRelayPassword Bad relay password
GameUI_Disconnect_BadSpectatorPassword Bad spectator password
And I think Kunkka and Beast Master got new attack sounds.
Also, TF2 like "Strange" weapons things will keep track of a number of stats. Treants made, Trees made, First Blood, Carries killed, Wards placed, Gold earned, Kills, Godlike Streeks, Gold Spent, Towers Destried, and Blade Dance Crits.