I paid the $75 with Paypal (they had a little paypal button on the wfmu page after I submitted my info) the same night I pledged.... was I not supposed to do that? They never sent anything in the mail, so I think they got it and it worked out ok....right?
Probably. If you paid it immediately, then you probably shouldn't get a bill. and you'll get the premium for the show you pledged to (unless you stated another preference, i think)
I paid my pledge with Paypal as well but I still got stuff in the mail asking me to select my DJ premiums and stuff.
that's probably because you are getting more than one premium.
Anyway, no one should really worry about anything. It will all get done, just maybe not instantly.