Sprint is cool. For me it enhances the experience of feeling like a super powerful spartan, being able to run and jump from A to B quickly. I wouldn't want to see a total reversion back to Halo 3 with regard to base player ability. I don't see the harm in adding a couple of extra options alongside attack/jump/strafe, so long as those options are the same for everyone and not a choice like the present use of armor abilities.
I'd like to see what Halo would be like if players had multiple armor abilities at once like Crysis 2. For example, make the jet pack into a jump pack activated by double jumping like many people have suggested (or maybe charge jumping), but have it be a base player ability along with sprint, both tied to the same meter, so you have to make a calculated decision for each use. This way everybody has the same extended mobility options and there's no guess work about what cheap tactic someone may resort to; if there's a raised platform you're trying to secure you always know that your opponent has the option of double jumping up to it instead of taking a ramp or a lift the long way.