I have returned A WINNER!
The whole process took 2.5 hours, of which the first one in line to have my fingerprint taken (they already took them for the Argentinian criminal record, but that didn't count...) despite having an appointment that read 12:00. There was a long, long queue, and just one booth with a malfunctioning scanner to take fingerprints.
Documents:
1) my current passport
2) certificado de antecedentes penales argentino
3) criminal record from my home country (Italy) apostilled in Italy and translated by a traductor publico in Argentina, whose signature was legalized at the Colegio de Traductores Publicos
4) certificado de domicilio argentino (that I obtained on the spot at the Registro Civil of San Isidro, partido de San Isidro)
5) one photo face and tip of the shoulder, facing forward and on white background (selfie with iPhone + photoshop)
6) Partida de matrimonio obtained at the Registro Civil where we got married (Munro, partido de Vicente Lopez), without further legalization of signatures
7) DNI of my spouse, my sponsor
*Birth certificate was not necessary because I was claiming permanent residency through marriage, so I just needed my marriage certificate.
About originals and copies. As suggested on this forum, I brought two copies of everything. I confirm this is no longer necessary since they scan the documents and they return you everything immediately. However, our guy was smart enough to scan the copy instead of the originals, so that he just needed to feed the whole bunch of A4 sheets at once, which made the scanning part faster.
He checked the passport copy very carefully, but scanned only until page 13 since from thereon, the pages were not relevant for Argentina (I just had two stamps from Tunisia on the last page). The copy were stamped as "true to the originals", but I suppose that was for the scanner and not for us.
About fees and costs. Paid ARS 600 (no Mercosur) for the application and separately ARS 40 for the DNI. Paid ARS 300 for the translation of my criminal record + ARS 145 for the legalization of the translator' signature, and paid around ARS 30 for the Certificado de domicilio. Paid about USD30 in Italy for my criminal record there. Overall, the whole process cost me around USD110 (at today's blue rate).
About the permanency. I was given the precaria immediately, it bears no DNI number. Our guy said the actual DNI should arrive within 90 days. My precaria reads it is valid 90 days (until January 29th 2015). On the TV screen in the waiting room it read that if you don't get your DNI before the precaria expires, you have to inquire with Migraciones (DNM).
Our guy said to keep the A4 paper with my passport until I receive the plastic DNI, and to show it for traveling abroad meanwhile.
About the whole process. The flyer linked in this thread describes exactly what it is needed. However I was expecting a faster dealing given I had to wait a month for the first available appointment. Saw many stalls and personnel but only a few stall had actual people working in them. Saw a lot of people standing and chatting behind, sipping mate and spreading cupcakes, kissing, etc. However, the people that attended me were extremely polite and smiley, totally different experience than with USCIS, where they look at you as an inmate rather than a person. Saw a giant poster of Nestor Kirchner that read "In modern Argentina, those illegals are only those who wants to be such" and found very heartwarming (though I hate the man) and welcoming. No threatening advertises about fines and imprisonment as in the US.
I should reconsider my views on Argentina.
THANK YOU forum members for your help!