I give her a lot of credit for that stunt. And as for being pregnant, she had a lot of energy on that stage.
One of the things I admire in Rihanna is her diversity, as every song is different and it is hard to categorize her music.
She can go from Hip Hop, to Jazz, to Old School R & B, Rap, New Age, Reggae, Disco, Adult Contemporary, electronica, and even ROCK!
The thing is, the Super Bowl may not be the best place to carry all these types of Musical Genres out live. Many of these genres can only be lip-synced and sung over backing tracks that don't sound all that good played over STADIUM PA systems!
You bring out a live band, set up the drums, and other instruments, played over their own sound systems and amplifiers first before adding the sound to the House PA, always sounds best audibly and probably best suitable for places like the Super Bowl half-time shows.
All things considered, last night's performance could have been a lot worse.