Depends on how verbose we want to be. It should say why one might want to 
use urandom() instead of random (if you decide you are interested you can 
still look up the documentation). I think it would be nice to say why 
random does not use urandom if urandom is better, so you end up with a 
very short pro/con of urandom, which should be appropriate for users who 
are seeking information on getting random numbers.

Unfortunately I don't know enough about random. I guess it's a 
speed/security tradeoff?