Thanks for the tips, and I'll now add my experience.

First, as everyone knows, flying Aerolineas is not a joy. That said, my experience was OK.

I was surprised by the long check-in lines at Aeroparque (although the fact that it was a Sunday afternoon, 3 pm flight probably contributed). It took about a half hour to get to an agent. After that, it was easy. Security reminds me of America pre-9/11. No taking off of jackets or shoes, and a more cursory review of carry-on baggage. You don't take your liquids out, and nobody questioned my water bottle.

Carry-on bags weren't weighed, and I did see one or two people with small roller suitcases on board -- obviously well in excess of 5 kg! Most folks check everything bigger than a briefcase. That said, I also saw one family with 3 cases of carry-on wine! Not sure how they got that on board, but as a foreigner, you don't ask too many questions.

Aerolineas' departure times seem "flexible." Not much hustling, and no updating of information. My outbound wound up about an hour late, but my return only about 20 minutes. The wait for luggage at Aeroparque seemed ridiculously long (like a half hour), but not much you can do about it.

Although both my flights were supposedly operated by Austral, I had Aerolineas aircraft on both occasions (MD-80s). The first plane had the least legroom I've ever seen on a jet: I'm not even quite 6 feet, and my knees wouldn't fit in a "normal" position. The return flight has slightly more legroom. Each 3 hour flight had a modest cold plate and beverages, including free wine and beer.

It would be great to have more competition, but it sure beat a long distance bus ride.