I pay $84 per year for a USPS mail box, it's one size up from the smallest. I find it holds magazines, letters, bills, and other junk mail more efficiently than a super cramped ghetto box.
If I receive a large package such as a DVD Player from 800.com they leave a "parcel pickup" slip in my PO Box, I take it to the counter or their will call (closes at 6PM), they take it and hand me the package.
The only downside is UPS and FedEx will NOT deliver to a USPS PO Box. But if you get a PO Box from somewhere like Mailboxes Etc. USPS, UPS and FedEx should all deliver to those addresses.