You are right, the functionality is identical in the cases you cite. But || comes with a *lot* of caveats when you use it in circumstances like this. The RHS of or will always be executed last (unless parentheses are used, or there is more than one or). This means if you want to say (psuedo-code):

  if (open fails) { die }
[download]

or gives you a way of writing literally that. || means something a bit different, and can cause considerable confusion. It's a bad habit and a maintainance problem to use the wrong operator for the job. See perlop.

Andrew.