Personally, I've always enjoyed the sprinting function and have to agree with The_Preacher, but I also think that the current run speed should be given a little "umph" and the sprinting function should be lengthier.
I haven't played BF2142 yet, so I don't know if this function is in it or how it works, but I like the ability to be able to switch from walking to running coupled with an additional sprint function (balanced properly of course). It could be quite good if done properly. I think.
Typically, sprinting gives you a finite mad dash ability while losing the ability to fire while running allows you to move at a relatively fast past at the expense of accuracy. And of course walking allows you the greatest accuracy while moving, but only at a slow pace. Balancing would be the key to all this. ;-)
Artificial intelligence is no match for natural stupidity.