[Marcor]

You can select the dictionary you want in the basic menu, say english or the english/italian transaltor (in my case). Then you have to activate it during the reading. To lookup a word you have to highlight the word (not just click on it) It really seems to me working very well, although not that fast. I personally am using a stylus for capacitative screens (I tried several and many do not work properly) mostly to avoid finger prints. I never mis-selected a word. What they really have to work on - aside of other things - are the notetaking and highlighting which are not usable.
As BD mentioned above after now barely two months I am very happy about this purchase. I read mostly e-pub and comics (pdf, or comic formats). Not all sort of comics do the same but I use it mostly for Bonelli comics (Nathan Never, Dylan Dog, Tex Willer,...etc) and they are black and white and the original size is just a little bit bigger than the 9" screen so it reads very well.
Again on the grey screen issue: contrast is not fantastic and in certain light conditions you might need a ebook light, I mostly read before sleeping so I was already using this.
Probably the PB903 does a lot better but it costs also 170 euros more (ca. 230 USD more than the DR900)