I hear ya!
Back in July I submitted a tech support request to ImTOO to let them know that although the AMD-APP icon was flashing, I saw no activity on my GPU and nothing rendered any faster.
I told them I had a Radeon HD7950 card and that I didn't see it on their list of supported cards and was wondering if THAT was the reason the APP functionality wasn't working.
"Sorry for the inconvenience. We will forward your request to our technicans, they will consider adding that."
So they never really answered my question. I have no idea if it SHOULD be working (seeing as the APP is flashing) and there is something else wrong, or if it's because they don't yet support the 7900 series cards.
Check the list of AMD-APP supported cards and see if yours is on it. If not, shoot an email to firstname.lastname@example.org and ask them about adding support for it.
It's frustrating that this APP technology has been around for awhile, yet it's still difficult to find anything that uses it successfully.
I gave up on my Giga-Byte Nvidia 560Ti because it would fail when using CUDA, and returned it and got a Radeon thinking I'd be good to go...no such luck
Let me know what you find out - I'd love to be able to take advantage of this feature too