OK ..... I took delivery today of my shiny new ASRock ION 330 and I've now had a chance to set it up and have a little play.
I connected it via HDMI to my Sony Bravia 40" TV, connected to my wired LAN, plugged in a Keysonic USB wireless keyboard and installed Windows 7 x64, took approx 28 mins and all drivers were found automatically, except one (co processor), so a quick look on the supplied disk fixed that.
I then installed Media Player Classic/ffdshow and accessed my 1080p .mkv fileson my main PC, via the Network. I'm pleased to say that all of them played like a dream, as well as some 720p files, no stuttering or problems of any kind. The Nvidia ION certainly handles things nicely. It does exactly what it says on the tin and is very quiet.
I've added AVG, SuperAntiSpyware & SpywareBlaster and M$ Office, plus a few other bits and the performance is quite decent. Probably not ideal for video converting etc., but very adequate for most things.
So far I'm very impressed and haven't found any negatives, but I haven't been able to test any BluRay disks yet, as I haven't got a BD Drive to plug in, although I doubt this will be an issue, if PowerDVD Ultra is installed.