Not sure how to feel about this. The core feature of the free Google Apps was that you could use GMail with your own domain without having to run a dedicated mail server yourself.
This method is actually far more convenient than setting up Google Apps. You can both send and receive mail at the other domain, and you get a unified inbox (which Google Apps never provided).
Google Apps for domains lets you point your domain's MX record directly at Google, and Google accepts the mail for you.
I can attest it takes about 5 minutes to setup if you already have web space somewhere and know how to access its email server details.
The fact you're using gmail will still be obvious to anyone looking at headers, but that's not really a problem.