Is that sales of the PC version only?

Unfortunately, no. I'm hoping for some kind of sequel or at least add-on as well.




No, it's across all platforms. From what I could gather 0.35m copies have been sold for the PC, 0.89m copies for the PS3 and about 0.97m copies for the Xbox360.

Sources:
http://gamrreview.vgchartz.com/sales-data/43322/deus-ex-human-revolution/
http://www.joystiq.com/2011/11/05/deus-ex-human-revolution-sales-show-who-will-dominate-in-the-cy/

I think they will milk all the DLC packs they can and as long as they are quality I'll continue to buy.

That's really not all that great for a big budget game like DE:HR.

The budget was largely spent for the console versions. The porting was likely rather cheap.

As for the AI, it's a specious argument. So, it has the best AI out there, but "oh, imagine if it was better." You could apply to that to anything. "Yeah, A-10C is nice, but oh, imagine if the graphics were even better". The iPad is the best selling tablet out there, but "oh, imagine if it sold even more." The SR-71 was the fastest plane to see service, but "oh, imagine if it flew even faster."

It was already mentioned that you won't get "real" AI in a game like this because testers find it too hard. These testers WANT to play at the hardest possible level and still beat it without undue effort (for them). If THEY can't beat it, then it's screwed up. It's the same with graphic settings. They're not going to make a game with graphics that need several YEARS before the hardware exists to make it play well. Crysis did that. Look how far that got.



The Jedi Master