Should I get an HD for my PS2???

[complexstatement]

Hey, im living in Brasil right now, and im just wondering, I have around 3 HDs hanging around, and i wanted to install one of them on my PS2, but im not really sure what use its ganna do, why put an HD on my ps2? ive heard of booting up games from the HD, but what other functions will it include, for those who already messed around with this feature and discovered new features, list all the possible things that can be done with an HD, just out of curiosity lol