I'm pretty sure the drivers are now there for Ion hardware acceleration on W7. I found myself with a Sling Adapter purchased on day 1 and no computer gutsy enough to handle the HD streams. So, based on the recommendation of another member here, I bought a Zotac Zbox with the Atom and 2nd gen Ion GPU. This manifestly works when I first start it up; 4 threads show around 97% utilization, video looks good. Then (I'm assuming) something else starts up and makes playback go to heck, with audio out of sync and video stuttering badly. It's basically unusable.
This doesn't happen with HD Netflix, which seems to use both far less network bandwidth and less of the Atom MPU power (more like 75%) to decrypt and decompress.