The usual caveats and disclaimers apply. What follows is a layman's opinion, nothing more, to be discussed with your physician if you think it is appropriate to do so.
My opinion is a big "maybe."
Typical opiate withdrawal symptoms include anxiety and insomnia. Benzos, in moderation, can take the edge off of the anxious and sleepless times. However, another common reaction to opiate withdrawal is depression and lack of energy. Benzos can exacerbate depression and if you are not anxious they will often make you more tired. For these reasons they may be counter-productive.
Nonetheless, for the reasons cited, I think Valium or other benzos can possibly be helpful during the initial stages of withdrawal. Because of their well-known risks I would hope your doctor would give you no more than about a week's supply. You don't want to substitute one addictive substance for another.
Also, IMHO, the agony and discomfort associated with opiate withdrawals is awful to go through but serves as a powerful deterrant to relapsing. If you are totally zoned out during the acute phase of withdrawal (i.e. the first 5 days) then maybe that important "lesson" will be lessened or missed.
Some places tout expensive withdrawal methods that leave a patient in a twilight state of anaesthesia, claiming an essentially "painless" withdrawal. This technique has claimed a few lives in the process. Whether or not a "painless" withdrawal is possible or even desireable is a good topic for discussion. I would love to see the results of any studies on the long-term effectiveness of the "painless" approach. Given no negative reinforcement, is an addict more or less likely to relapse?
More good research is needed.
Buzz