I think one's attitude to biking in BA depends on where you come from and your experiences. I was used to riding in NYC, so biking here is no big deal.
Yes, occasionally the buses or taxis get a bit rude but for the most part, I've found the drivers to be respectful. Not exactly gracious - they won't give you right of way the way they do in Europe or California, but they generally have the attitude that we're both there to share the road. You just have to be assertive, claim your space - and they'll honor that.
There's a lot less honking here and crazy drivers than in other Latin American countries.
I have a thick cable-type lock ($60) plus a smaller one ($20) that I use to lock the seat to the frame, and I've locked the bike all over town in every neighborhood for hours at a time and never had any problems. Never overnight, though - that would be inviting trouble.
I like what MizzMarr said about life before and after getting the bike - it made all the difference to my quality of life here. I can get across town in half the time it used to take me on the buses or subway (or even taxis - at rush hour, I fly past all the traffic). Plus it lifts my spirits and gets the endorphins flowing.
If you want to ride with a group, Critical Mass ("Masa Critica") meets at the obelisk the first Sunday of every month at 4pm for a huge group ride.