Personally, I have "pirated" in the past but it was just downloads of stuff that wasn't otherwise available (NES games, TG16 games, SNES games that were never released in NA, etc.) If you can buy a new copy of something there really is no excuse for pirating it.
I can see the PC game pirated as demo issue, though I can't really condone it. I would imagine that for everyone that says they are just downloading something to try it out or see if it runs, there are probably 3 more who do it and then play the game through and never buy it. Does that mean the game would have been worth a purchase? Not necessarily but you did still pirate the game and play it, regardless of whether or not it was intended as a "test."
DRM scheme got you down but you want to play the game anyway? Too bad, just don't play it. Overly obtrusive DRM schemes are garbage, yes, but gaming is a form of entertainment, it's not like eating, breathing or drinking water. If there is something you don't like about a game then don't play it. All a game company sees when they look at their stats and see 1 million retail sales and 3 million pirated copies is 4 million people they can sell their next game to. They are not getting the message that pirates are supposedly trying to send by whining and yelling about horrible DRM and then playing the games anyway.
Hey, that Ferrari looks sweet but I can't afford it.. guess I'll steal it because there's no way I'm going to go without driving it! Sounds pretty stupid, right? Yes, in many cases games do cost more than they should. Or, to me anyway, they launch in general at reasonable prices but don't decrease in price appropriately as they age/underperform, which is what happens with pretty much any other consumer product on the market. Does that mean they should be pirated? No. As before, just don't play the game. Be more choosy about what you really want to play and realize that *gasp* it's not your god given right to play every single game ever released. Wait until a game goes on sale, borrow it from a friend who has purchased a legitimate copy, maybe just don't play it at all. You won't die if you can't play Super New Game X near release, or maybe not play it ever, really you won't.