Traditional Islamic jurists have been unanimous in rejecting the idea that this verse gives a man permission to physically assault his wife in order to harm her. Those jurists who have allowed the man to strike his defiant wife have insisted that it be done no more than once and that it be no more than a light tap to express disapproval. (See Ibn 'Abbas's ruling of using a toothbrush, for example.)
Other jurists have said that the word daraba in this verse is to be understood as separation. If a man feels hostility from his wife, he must cool his anger by leaving the house (possibly leading to a divorce, which may give the wife pause for thought and leave room for reconciliation). Those who favor the second view point out that this is the process that the Prophet followed when he was having trouble with some of his wives (who were disrespecting him over his self-imposed poverty).
The Prophet is the model for how to interpret and implement the Qur'an, so we need only look into the three-step process he followed to understand how to apply this verse here in question. (See 33:21)
When he was facing defiance (nushooz) from his wives, the Prophet first talked to them; then he boycotted sleeping with them - for an entire month. Finally, when they kept vexing him and treating him in an unreasonable way, he offered them a divorce. (See 33:28-29) The Prophet went through all three steps outlined in this verse, and he never laid a hand in anger on any of his wives. A'ishah said, "The Prophet never beat any of his wives or servants." (Ibn Majah, Nisa'i)
The Prophet also said, "No Muslim man should ever hit one of God's female servants." (Abu Dawud, Nisa'i, Ibn Majah) A man named Mu'awiyah went to the Prophet and later reported this exchange: "I went to the Messenger of God and asked him, 'What do you say about (how we must treat) our wives?' He replied, 'Give them food like you have for yourself, and clothe them with what you clothe yourself, do not smack their faces, and do not angrily ignore them in public.'" (Abu Dawud)
So it is clear that both the Qur'an and the Prophet categorically forbid the harming or physical abuse of women. Now looking at this verse even closer, since daraba is used here in the singular (one-time) verbal form and not in the intensive (do it repeatedly) verbal form, it's also clear that it could hardly refer to a physical assault. Who hits somebody once when they're beating them? Yet, a separation or a divorce from a spouse is something that is done usually only once, if ever.
During his last pilgrimage, the Prophet said, "Be mindful of God regarding women, for they are your responsibility. You have rights over your spouses, and they have rights over you. It's your right upon them that they not let anyone you dislike enter onto your bed and that they not commit open lewdness. However, if they do that, then God has allowed you to ignore them in the bedroom and separate (daraba) from them, without committing violence (i.e., by not assaulting your wife)." (Muslim)
Therefore, when interpreted with the Prophet's application of this verse, coupled with relevant Qur'anic and hadilh references, this verse actually forbids abusing women at all and instead counsels trial separations (perhaps leading to divorce) as the last resort open to a man who is utterly dissatisfied with an incorrigible situation.