"encrypt your download links to prevent leechers" -- "encrypting" links with this would be a pain in the ass when you can't perform the reverse process.
Increasing the alphabet for passwords doesn't really make your password stronger than if you would just increase it's length by a character or two, or better yet three or four. But, given that I can't imagine too many password crackers checking for more than a couple common extended characters, it's probably not that bad. Still doesn't excuse passwords like pɹoʍssɐd though.
Every password manager I've used (granted only a few) will generate random ones for you. Is this significantly more secure than a random 18 character string?
These characters aren't easily type-able and most password crackers that I've seen use common ascii/ansi characters not obscure characters like this... It's all relative I guess. There obviously exists a case where these characters aren't helpful.
Can you realistically crack an 18 character random string, even if you know the character set? I mean, I realize that technically increasing the character set would make it harder, but for any web-based service cracking something with 62^18 (or more if other characters are used) possible combinations is impossible in the real world.
Because it's awesome. It may be subjective but it's the weekend and it's a cool site.
It's useful for passwords if you use a password manager or equivalent technology.