The DM900 is going back. I am copying and pasting this from what I sent in a conversation with Spoons.
The DreamOS based images are just about OK but the whole thing feels slow for some reason and the remote isn't that responsive and you really need to point it at the receiver. With the Mutant I can point it anywhere in the room and it will register it.
There are some other minor but highly annoying niggles. With DreamOS, there's no real possibility of setting automatic language for sound and subtitles look horrible - like they did in the very early days of Enigma2. I am sure there are plugins to work around these but meh... it should be like this out of the box!
The OE-A based images, such as OpenATV are somewhat better and are usable but some niggles, such as not being able to do GUI scaling is a huge one. The option is there but it adjusts the video behind it, rather than the GUI! As a result, with overscan switched on the TV, I am clipping GUI and with overscan off, I get crappy black bars and general rubbish around the edges. Second annoyance is that there's no way to switch on "black screen" during zap. It will keep the last played image instead of turning black. Again, there's an option for this on any other receiver but not here.
The unofficial OpenPli image is full of silly bugs, such as the right cursor button doesn't work on some menu items, so I have to use the left one to scroll through all the available options to come back to what I want.
It's going back and I am going to live with the slow lock issue on the HD51 - as that's the only issue with the Mutant. Which is a shame as the DM looks very well built, very sturdy and solid. Just the software side that lets it down. Massively.