Yes, having withholding is a very good idea.
For purposes of avoiding tax penalties, you must pay into the system, either from withholding or estimated payments, an amount that is either:
a. 90% of this years' tax bill
b. 100% of last year's tax bill
c. enough that you owe less than $1000 when you file your return.
If you make estimated payments, they are considered made when you make the payment, and if you miss a payment, you can be assessed a penalty for underpaying the estimate even if you catch up. However, withholding is assumed to be paid evenly throughout the year. This means that if you never make an estimated payment during the year, and make a final estimated payment on 12/29, you can be penalized for under-payment; but if you make a withdrawal on 12/29 and have sufficient withholding to cover your taxes, you won't be penalized because you are assumed to have made withholding throughout the year.
It may sound odd at first, but it means that withholding is generally better for avoiding penalties than making payments.
