Re: Dota2 replay
/Steam/SteamApps/common/dota 2 beta/dota/replays
If you wanna play 523434.dem for example, just use "playdemo 523434" in console
They are quite big... biggest is 100mb for me Oo
There is no autosave for own games, just the ones you downloaded.
But they already said (blog) that they will change replay-format next week, so I guess they will be smaller then