[4.0] Purchase Requisitions

I would like to implement this feature in our company, but I am not sure on
how it is going to work. For instance, you must check your "to do list" at
least daily if not several times a day. Also, if someone is out that must
approve the requisition, what do you do then? If anyone is using this
feature, I would like to hear from you. Any input would be helpful.