Since we’re most likely getting the Halo 2 incarnation of the BR in Halo 4, we can only expect it to be amazingly powerful. When asked about the Pistol in an interview, Frankie said that 343 has a certain love for the weapon. Since 343 isn’t stupid, and will most likely balance the rest of the weapons with the BR at the center, we can expect very rapid kill times.
The only reason Sprint was bad in Reach was because the DMR killed just way too slow. With the new BR, it will take 2 shots from a pair of players teamshotting. Unless a player is already near a corner, he will most likely not be able to run away. I really see no issue with Sprint now, and I just felt the need to bring this up. My only major complaint after some thought is the idea of having armor change gameplay, since I hated the idea of loadouts.