I tried using a mail forwarding service for the first time this summer when I was on vacation. I submitted a change of address to the Post Office to have things sent to my private forwarding service. They would hold my mail until I asked them to do a bulk send to me. They did their job and things worked fine with them, but the Post Office end was a disaster. First, the PO only forwarded what they thought was First Class Mail. Fine, but their method of determining First Class Mail was hit or miss. Apparently business size envelopes (#10) that have a lot of extra verbiage on the front were tossed out as 4th Class mail. That included some of my normal monthly bills. Then when I got back home I tried canceling the PO mail forwarding. They deleted the forwarding address but didn't clear the forwarding "flag" for their auto-sorting equipment. So any First Class Mail that had the address bar code on it allowing machine sorting was kicked out for forwarding to a non-existant address. It took multiple trips to the PO over about two weeks to get that resolved. Luckily that mail just rode around in the delivery trucks for a few weeks and finally showed up at my house when they got everything straightened out.
In the future I'll just use my very friendly neighbors and my garbage can size mailbox. I can go 3 or 4 weeks collecting mail in my mailbox now, so having the neighbors pick it up every week or so isn't a problem. And I've figured out how to get electronic (e-mail) notification of all my monthly bills.