I have purchased this piece of Home Theatre goodness:

http://darbeevision.com/darblet

And I can honestly say that it is worth every cent spent. Usually you see before and after shots of this type of Video processor, and find that it is smoke and mirrors (AKA Photshop etc). But this does do exactly what they say it does.
Makes viewing DVD's a pleasure now, and works great on local Satellite TV.

I have it as the last item in my chain. Between the Marantz and the TV. So the Oppo, Raspberry Pi (Xbian) and Sky decoder all run through it. I find that it does a far better job of Video processing than the Oppo built in processor. But I know see that the new Oppo's now come with the Darbee built into them.

The Darblet appears to be a kind of "selective sharpening" filter. That is, it provides sharpening, but only does so on selective parts of the image. For example, it brings out detail in things like hair and wood grain, but does not cause excessive ringing on other parts of the image.

I have read, and have found myself to agree, that a good "universal" setting is "High Def" with a value of 45.

That being said, I did experience HDMI handshaking issues. I use a Crystalio scaler, and I simply cannot get the Darblet to work between the scaler and the TV (the most ideal setup). I get about a .5 to 1 second video blank every 10 seconds, and, it will not pass audio from the scaler. I'm currently trying to get some diagnostic data to send to the manufacturer to investigate this further (using a Quantum 780, which I'm still waiting on). I can use the Darblet between my cable box and my scaler. However, every time I power the scaler off, it resets the HDMI audio options on my cable box, requiring me to have to go back in and reconfigure it every time I power the scaler back on. Very annoying!

Another thing to keep in mind, is that if you are using it with video that has already been sharpened or remastered, it may oversharpen the image.