I don't see an issue with pirating games if you intend to buy it.
I wanted to see if CIV 5 was any good compared to Rome. You can never tell from the videos so i pirated the feck out of it thanks to TPB and played through one 100 turn map. (so about a couple of hours worth of demo)
Turns out I loved it so happily paid for it but whilst I waited for it to arrive I played my pirate version then swapped my files over when I got the real one. Same with Walking Dead and multiple others.
About 80% of the time I end up buying the game anyway within a week. If i don't buy it then they failed to impress me. (Plus a lot of games don't have demos

)
I also don't see a problem with pirating games I owned at some point in the past - for example I have the original AOE collectors set but can't for the life of me remember where the disc is, so naturally TPB was my first port of call. (GAME wanted like 4 quid for it!)
My argument against the popular flames I get:
- "Use canyourunit.com to see if you can run it"
That site is terrible for some games and depends on your personal setup. It can give you a rough indication but can't tell you what the experience will be like for your card/resolution/CPU.
- "Download a demo, noob"
Demo's these days aren't really any good IMO(If available at all!). I've often tried to play demo's for games I now own and love and had really bad experiences - I was surprised to find out that for one game I had (some shoddy FPS), they had used a beta build for the demo!
(I want to say Bulletstorm but I don't think it was)
- "watch a letsplay"
...and ruin the game/story? No thanks.
- but it' been reviewed by XXXX
I don't trust reviews for the most part and like to form my own opinions. Plus, sites like IGN etc give everything good reviews!
As a bad analogy, would you buy a shirt in a shop having only been allowed to try on the sleeve? The makers of it told you it looks amazing, and the reviews of it from random strangers say the same... you wouldn't buy it would you? You'd want to try it on, check it out properly before committing to a purchase. - plus you can't return open PC games at most retailers.
I think it comes down to honesty. If I like a game I've pirated then I will generally buy it.
The main issue for me comes down to not being able to send back opened PC games (or trade them in in most places!)