Hi Fred, I have had my QHY9 for a while now. I think mine was one of the first shipment to Australia and I am very happy with the overall performance of the camera. The 8300 CCD does exhibit a lot of hot pixels but these are easily removed. As for sensitivity it is great. I am pushing it quite hard running at 0.65 pix/ arc sec with my VC200L and the results are quite pleasing.
The backup and after sales service from both QHY and Theo are great. The smallest glitches are investigated and usually corrected the same day. Most of the early teething problems and software compatability issues have been addressed so the camera will now work with most major capture programs.
1.25" filters, I don't know as I have only used 2" filters and have only had them a short while. The Filter wheel is great and is fully integrated with the camera control.
Examples of my results with this camera can be seen here.
http://www.darkskyau.com/cm/thumbnails.php?album=27