The timing of the transfer of property interests is very important in Maryland. If you were to accept a quitclaim deed from the ex-husband to yourself, you and your wife would own the property as "tenants in common." Tenants in common have no rights of survivorship (e.g. if your wife dies, her share in the property does NOT automatically pass to you), and can freely convey their interest to other people ("good morning honey, I sold my half of the house to the neighbors").
If you are interested in immunizing you and your wife from liability in general, I suggest you execute a deed from your wife and her ex-husband to your wife and yourself. By taking the property at the SAME TIME, you will own the house as "tenants by the entireties" (T by E).
By owning property as T by E, judgments and liabilities of the individual cannot attach to your marital home. For instance, if your wife accidentally hits someone in her car, and owes that person money as a result, the victim cannot attach the judgment to your home if it is owned as T by E.
There are many benefits to owning property as T by E rather than "joint tenants" or "tenants in common." I suggest you consult an attorney before you execute any title instrument.
Even if the ex signs a quit claim deed, he will not be taken off of the note.
However, as long as his name is taken off before an liens are recorded, your future interest will be protected.