This is another example of how varied ones experiences can be in any given situation.
In my 3 years here I've never had any bad experiences with taxi drivers.
I've been burgled twice, hustled by the police, pick-pocketed on the subway, had bags stolen on a bus journey - but cab drivers have never been anything but honest and helpful.
In my experience, all remise agencies are trustworthy. Their only sin is that sometimes they will promise a car in ten minutes, and it will take twenty.
For those new to BA: remise agencies are car-owner co-ops. Unlike radio-taxis, owners drive their own cars or those of friends and relatives.
When you call the agency, the dispatcher quotes an estimated fare price (generally accurate to within 10%), and sends the next available car. When they arrive, Remiseros ring the doorbell and identify themselves and their agency. They don't pick up passengers on the street, but must see them get out of a home before letting them into their cars. Once they know you, you'll get a client number and can then request rides from stores and restaurants.
Remiseros compete among themselves for clients. They are polite, clean, and won’t blow you out of the window with the radio going full blast. Many drivers are unemployed professionals - I was twice driven by young architects, and another time the driver was so elegant and so cultured that I had a hard time deciding whether to tip him or not - felt like tipping the Pope.
Locals often develop a "relationship" with a driver, who becomes an on-call chauffeur. Some people are driven to work daily by their remiseros, or have their children picked up from school by them.
I live out in San Isidro, and often send remiseros to bring friends for a visit, pay bills, and take care of stuff I don't want to deal with. They drive me to weddings and sleep in their cars until the party ends. They take my dogs to the vet, and also run errands downtown, like getting the dogs' travel permits. Once I did eleven "tramites" in a single afternoon, with a remisero acting as a private chauffeur. It would have taken three or four separate trips to get that done driving my own car.
In my obviously biased view, remises are a great Argentine institution. Sorry for this long post, but newcomers may not familiar with them.