Software piracy has actually helped the marketing in many cases that I know of.
First of all, let's have a look at the professional 3D modelling, grahics... etc.
Those programs costs huge sums of money, I mean, alot.. you could for example buy a car with the price of most popular professional 3D modelling programs(!).
How many people do you know who would pay as large sums for such a program, without much knowledge about it?
I know some 3D modellers who have used pirated software and then taken it to their profession once learned to use it and got became able to make profit of it - and bought the program they've used 'illegally'.
I'd say most of these persons I know, wouldn't have done so if they wouldn't of had the program 'for cheaper'.
Most of all, they were all students at the time they began using the program...
I'd like to see how many students would otherwise have the will to buy a program worth a car, without any knowledge how to properly use it or even knowing it could someday become their profession.
Then I can talk for my own behalf with the pirated games..
I've downloaded games, not alot, only the ones which I think I'd like to play and then later on bought the games when seen it's worth it and didn't fly into the byteheaven the next day.
Although this can be partially accredited to warez games becoming available from couple weeks to couple months before available at the local stores, over here in Finland
..can't either talk much about trying the game with demos, since most of the games I've bought, simply never has had any demos to try!
Besides I hate demos.. when those are available for good games, it gets helluva annoying to wait for the full game... US OFP fans could probably second that

(for those who dont know, it was like closer to 2 months later available in US than EU)
and it's too damn pity not everyone can be rich.. windows alone has cost few times more the cash I have left in hand every month after the basic bills.