While I don't personally have a reason to use this, I'm sure a lot of people will find it quite useful.
One suggestion though, the user should be able to select their own URL if possible, and if they want to. I know it'll pose some security risks, but having a totally ridiculous address is going to make your notepad less than memorable.
There is a link to change the URL below the notepad. It validates and confirms that the name isn't taken and then renames your notepad and redirects you.
Alternately, you can just visit any URL you want and (as long as it's available) start using it.
One suggestion though, the user should be able to select their own URL if possible, and if they want to. I know it'll pose some security risks, but having a totally ridiculous address is going to make your notepad less than memorable.