I myself only use miles to upgrade international (no vips ) or booking international AAwards. I feel that domestic flights are so cheap, I get much better value on international itins.

That being said, if I had a $600 domestic fare, I might use miles.

As you have the cert (which if you look at the relevant thread, most here considered pretty useless), I would say go ahead and use it while you can. The conditions on it are rather tough, so get some value from it now.