I am absolutely no friend of touch screens and I am in the group that thinks that current ebook reader makers should not omit the buttons but dictionary lookup is one of the things where touch screens really are vastly superior to buttons. Believe me, if you had the choice and both possibilities on your reader you would never use the buttons for dictionary lookup.
I have the same kind of dictionaries on the Cybook Gen3 and I use them very often. From the content I am very satisfied, the handling, hm, after many many clicks with the buttons you have reached the word you want to have translated.
For German-English/English-German you can find an interesting and free alternative here:
http://blog.mikeasoft.com/2011/01/05...or-the-kindle/