Just got an email from Stardock about this deal, is the game worth it? I kind of liked DotA back in Warcraft and I've played some League of Legends which is the other spiritual successor, how does this measure up?

I'm not sure how it compares since I've never played the original DotA or League of Legends, but I remember being interested back at release and I took advantage of the $5 deal on now.  I played a bit last night and it's fun, although it looks like you'll really want to find other people to play with.  I didn't test the online waters, but in single player you can play with AI teammates against AI opponents.  My AI teammate was pretty bad compared to the opposition, and combined with my own inexperience, it led to a long game against the easy AI.  I'm hoping to put some more time into it.  We'll see how it goes.
 
Corvall