For those contemplating applying for their TIE. I attended the foreign office in Alicante yesterday.
When entering your information in the ticket machine, if you registered using your NIE, use your NIE. Vice versa for passport.
For those concerned regarding the need for Spanish, don't worry. In room 3 [sala 3] I found that all of the processors [there were 5 desks] spoke English. Even the security guard at the entrance knew enough to say "show me your appointment!"
They seem to bring everyone in batches of 5 - I was only halfway across the hall when called "please come, please come", so move quickly if you happen to be the last in your time batch.
The most difficult part of the process was taking the fingerprints. Alcohol wipes and several retakes, otherwise entirely painless process.