answered a set of frequently asked questions on Dota 2's official website, clarifying and detailing a few concerns players have had since the game's official announcement. Much of the questions revolve around players leaving games -- Valve has not only implemented an AI system to take over for missing players, but players will be able to have a "friend of similar skill level" jump in and take over if necessary, or simply jump into current games that are missing players. The bots will also be customizable, so if you want to play against an AI that tests a specific part of your game, like "denying, last hitting, and harassing," there will be specific configurations to challenge those.
Replays are also mentioned -- players will be able to examine games in progress from all sorts of angles, watching charts and graphs in real time as the game goes on. There will also be "commentating and editing" features for replays, and the game will make extensive use of the Steam Cloud, keeping keyboard preferences, replay files and other settings available from any computer.
Icefrog also says that there won't be any changes for the sake of change in the actual gameplay, and that he will continue development on the original Warcraft 3 mod "for as long as the community wants," but that Dota 2 "represents the long term future for the game." In that sense, Dota 2 sounds like a very direct translation of the original game, though Valve is sparing no expense in adding metagame features to make it a smoother experience for everyone.