We had read about the BRT before arriving in Rio but we didn't know much about the service. We saw the station at arrivals and it seemed to be popular and rather full. We weren't sure about using the service while carrying our luggage and daypacks.
Now we know and next time we'll definitely consider taking the BRT. As it turns out, there is a BRT stop right outside the hotel we stayed at near the convention centre and we could have gotten there for a pretty cheap fare.
First, you have to have a prepaid card to use the BRT. Stations do have machines so you can buy or add to your card but they wouldn't accept our foreign credit card. You can't use cash to board the BRT. I didn't look but I presume the airport station might have a manned kiosk where you can buy a card with cash. A couple of days later I did find a manned kiosk at Barra Shopping where I could buy a card from a real person using cash.
I kept calling the BRT a train because that's what it seems like. It has a dedicated lane and the stations are more like train stops with raised platforms and sliding doors. We rode them mostly in the Barra area but after getting on the wrong train we did head out into other parts of the city on an express train but we simply got off, crossed the platform and caught the next train going back. It's simple to change trains and once you're on the platform you can catch any number of trains going in different directions.
The only drawback is that it doesn't go to Leblon, Ipanema or Copacabana but you could transfer to the Metro.
The BRT can be crowded but we didn't feel unsafe at all. There is a place at the back of the bus where there is room for luggage or large items.