In my experience Steam releases have fucked up the game .exe more than any crack with a malware out there.
Valve games work well in Steam, that's about it.
Imo, that's exaggerating. Although it's not uncommon for users to have different experiences. Some games work great for some computers, others won't even launch. For me it's very apparent when I lurk around on the forums.
There's a lot of games that works like crap on Steam because they either don't have comparability for newer OS or they're just bad console ports, but there are also a lot of games that work just perfect.
Dead Space, Batman Arkham Asylum, Modern Warfare, Mirror's Edge, Bioshock and Mass Effect all worked great from the start.