Air assists don't work, not on the angel. They look cool, so that's always a good reason to get one, but they do jack.
The intellifeed my spin the paddles slower, but it spins them with every shot, so there's always a fresh stack ready to fire. So given the choice between that and a standard revvy, I'd take the intellifeed.
I have a HALO B on m IR3. It actually does have a problem with the HALO overforcing the balls into the breach. What happens, is because of the pressure on the stack, the ball rolls behind the cops rod, and an other ball partially loads into the breach. When you fire, the bolt pushes the ball behind the cops rod forward, shredding it, and sometimes also cutting the partially loaded ball in half, causes many breaks and not much fun. However, if you sand the cops rod down just a hair and oil the belt on the drivetrain of the HALO, this problem can be overtered. On the LCD's, it's not as much of a problem, because there's no cops rod and less room for the balls to roll back (or at least that's how it has seemed in my experience). For an IR3, you might be better off getting an eggII.