I was in the same situation 2 years ago as you are now : French reading novels in English and tired of looking up words in my 8 pound English dictionary.
I lingered for a few month, disappointed by a test of the PRS-600 (glare, difficult to use the touchscreen and inability to change the dictionary).
Then I waited a few more months for the iRex DR-800 which was promising but they finally dropped the dictionnary support at release time, sold it at 500€ and finally went bankrupt...
Tired of waiting I finally I bought a Booken Cybook Gen3 because of a good discount price (cf. this thread http://www.mobileread.com/forums/showthread.php?t=75280
I've been happily reading on the Cybook for 18 months now so here's what I think is important about dictionary support :
- You want a touchscreen for a seamless lookup. The Cybook has a D-pad, so the lookup is cumbersome and too disruptive in the reading experience. I still use it maybe once every 50 pages when I'm desperately curious about a word, although actually need it maybe once per page.
- Be careful that the touchscreen doesn't decrease the screen quality, maybe a transductive screen with a stylus is the way to go if you can bear reading with a stylus in your hand ! (something like the pocketbook Pro 603)
- You want to be able to chose your dictionnary. I guess many disctionaries are not suited to your own needs. For example I want a good fat en-en dictionary, I don't care about a small en-fr one that knows less words then myself
- You want either a clever dictionary or a clever device for plurals or word variants: for example my Cybook loaded with both the Webster's and Wordnet cannot find "apples"
- I can't speak for yourself, but you really don't want an LCD !
- One last thing to consider : it's very difficult to be honest and buy ebooks in English because of those stupid geographic restriction, so be prepared to get around those (e.g. having a friend in the US buying them for you)
This being said, I can't help much more because I'm now in the same situation as you are : I'm looking for the same, without the drawbacks of the Cybook : better dictionary support, a slightly better screen wouldn't hurt, lightweight, I don't care about color, wifi or 3G.
In conclusion I'll follow this thread closely and hope more will pop in !