AJ wins the internet.
The secondary fire allows you to fire a normal ring instead of the weapon powerups. This allows you to fire normally under circumstances where it wouldn't be to your advantage to use the weapons, like if you're in close range and you have a Rail. Note that the delay still occurs, so if you fire a rail, you can't fire normally until you would be able to fire a Rail shot again.
Although it sounds like a simple change, it really helps add more depth to the gameplay, since you no longer have to decide not to pick up the weapon ring because you're not very good with the Rail or Explosion, and can only use the special weapons when the time is right.
Having played with it a slight tad in match, I'm really quite happy with how it turns out.