I've never played DOTA, heard about it before but I kinda skipped Warcraft III so never really got into the mod scene for it but after reading that I really want to. Will have to track down a copy of old crafty when I get a chance - doesn't sound noob friendly tho so if anyone else wants to explore with me feel free hehe.
The guide and coaching systems also seem really interesting as they sound like a "community toolset" rather than developer built tutorials/content. I don't think I've seen anything like this in a game before:
Interactive guides will allow players to do more than just read a guide for their favorite hero that has been deemed helpful by the community at large. Valve plans to allow guide-makers to tie their work back into the game by doing things like highlighting suggested item purchases or displaying useful information during a match.
Finally, a coaching system is being deeply integrated into the game. By logging in as a coach, veteran players can do their part to help out newer folks. Valve hasn't entirely decided on the specifics of how newbies and coaches will be matched up, but once they're together a few things happen. The coach sees the pupil's screen, and gets private voice and chat channels to communicate with them. The coach probably won't be able to take control of anything directly (once again, the details are currently under discussion), but information is power in Dota 2 and having a mentor whispering in your ear can make all the difference in the world.
Also loving the art style they've developed in those characters thus far. Kinda weird for Valve to be doing a fantasy game with elves in it though.