There's that, to a degree. But <argument from authority> PG says smart people don't think they're smart, they just can't understand how dumb everyone else is</ argument from authority>. This doesn't mean they go around telling people they suck, but that's generally the attitude at Hacker News. You often hear about criteria being about whether something sucks or doesn't suck.

Also, being pretty good implies being better than others. Whether you praise yourself or dis others, you're still saying you're at a high percentile. Being good or sucky is relative.

PG and I are saying the same thing, essentially.

The difference becomes demonstrable when arrogance makes you ignore emerging threats and opportunities in the market. They say, "The bigger they are, the harder they fall". So, if you let confidence blind you; you are actually being arrogant.

I do not think 37signals or Jobs is blinded by their confidence. Though one could easily claim Jobs confidence led to his downfall in 1987. He even explained this at the commencement speech at Stanford (I think).