Sure, I took job hunting 101 too. I've also been involved in a lot of hiring decisions and a number of these sorts of discussions.

The gap in your chances between "I know someone in the company" and "I don't know someone in the company" is so huge that I can't/couldn't imagine a cover letter making a big difference if you don't already know somebody. So my recommendations have normally been around networking or canvasing friends-of-friends to know somebody and then go that route.

That said, I have to admit it's been a long time since I've had to do a cold round of applications so I totally accept I've underestimated.