I´ve been using mailboxforwarding for about 9 months and haven´t had any problems with it. Using their pdf scans I can get away with hardly forwarding any paper mail to myself. I´ll probaby keep using it even when I´m not moving all the time just because it is so much nicer to have all my mail in electronic form. When I was researching the mail forwarding companies I made this site to compare the prices, addresses available, etc.
http://postalmailforwarding.com