I've overdosed on aspirin a couple of times. Not as a method, but like dead_inside said, a supplement. I've never calculated a lethal dose, I just take the full bottle of whatever I have because I don't care about taking too much, I just don't want to take too little.
There's evidence of damage to my liver, and I had 3 days of ringing in my ears and cramps and nausea after one overdose. But never anything close to death. Just discomfort.
Altho based off the discomfort I've felt from high non lethal doses, I can't imagine it's very pleasant attempting to die from an aspirin od.