It looks like an interesting machine to me. The big problem (particularly using it as a Hackintosh) is the reliance on the GPU to make it fast. The Apple TV does that too, yet there is no way to take advantage of the GPU (unless you run Linux on it).
If the programs aren't written to use that GPU acceleration, then they will be slow. For me, I want to use my HTPC as a DVR *and* a HTPC. Part of that plan relies on the machine being able to serve the recorded files via iTunes (ideally to my existing TV). For me to push them out to another AppleTV, I will need to re-encode in an ATV format (something that an Ion will never do well). This would include HD recordings.
If I weren't considering this DVR side of the equation, then the Acer would easily be number one on my list.
Scott