Rabbit Run seems a most incongruous of spells, one of limited use to any but those who prefer their vegetables raw. Nonetheless, this is an excellent spell for both defense, unseen exploration, and getting into and out of tight spots.
Rabbits are among the quickest, nimblest and most agile of creatures. By transforming into one, a mage can easily dodge most humans or large beasts, either with speed, a sudden hop, an impossible seeming change of direction or a quick bolt into a tiny hole. Rabbits are quite attuned to dangers, and one who transforms into the furry shape attains much of that sensitivity. One can recognize the peril much sooner than in human form and scoot from it before it gets too close. Once safely shrunk, the mage then has the freedom to explore where he or she dare not stick an arm or head. The safety of a bolt hole also allows time to plot new strategies or consider further transformation. It is not considered wise, however, to turn into something much larger whilst sequestered in a small end enclosed space, especially underground.
Many feel that rabbits, because of their quickness to flee or spook, are cowardly creatures. Nothing could be further from the truth. Their hind feet are quite strong and have been known to knock other rabbits, cats, small dogs, or snakes senseless.
Against other opponents their own size, the advantage of being a rabbit shrinks. What good is it to dart into a tight hole if you're fleeing from a hungry weasel or fox? In times like that, a dead-end burrow can become exactly that as the unfortunate spellcaster ends up dead. 
- ↑ KQC2E, pg 225, 226