The issue of whether it's worth the extra $100 is really in how you like the extra processing. I purchased the Darbee Darblet some years ago and put it between my Anthem AVM50v and HDTV. I found that the Darbee's processing was the same as applying an aggressive unsharp mask to the video image. You can adjust the effects, but it can make things artificially hyper-sharp. Where it was very effective was background stuff like the audience in a stadium or grass blades, etc. If you look at the demo images on the Darbee site, the after images are (in my opinion) too aggressively filtered.
In general I would say the following: If you have a good pre-pro with good processing then you may not be all that satisfied with the Darbee. If your pre-pro has nothing at all for video processing or scaling then yes, you may like what the Darbee does.
I ended up returning it because I didn't feel like the price justified the value when I was getting a great, natural-looking picture through the Anthem.
