I do this with ImprovMx. You set up the inbound to forward to some other address. For outbound you can either pay them or set up GMail to do outbound aliasing.

I do this with ImprovMx. You set up the inbound to forward to some other address. For outbound you can either pay them or set up GMail to do outbound aliasing. It works fine for me, but there is some lag on inbound emails.