I have a PO Box for my work mail. A PO box seems like a great idea - get an address that's independent of where you live (or where you work). You can either go and collect the mail that gets sent to your box, or have it delivered to you. I opted for the latter (at an extra cost of about £50/year).
I've now moved about 5 minutes walk down the road. That puts me in a 'different postal zone', so the mighty Royal Mail can't manage to deliver my mail to me, so I have to apply for a whole new PO box. What the hell was the point of that? If I've got to reprint all my stationery every time I move, I might as well not bother with the PO box!