After some bit of studying, you find out that romaji tends to just get in the way. So stay away from romaji dictionaries- luckily I've never really found any (except as methods of input). As someone in another forum said, "kill the crutch."
I have a wordtank G55. Here are the features:
Jump: already discussed, lets you go to words you don't know the pronunciation of or meaning of and look it up. Very useful
Also, as I'm sure is the case with most dictionaries, you will usually have example sentences with the definitions, so the thing about context is a bit of a moot point.
Aside from the Jap-Eng-Jap dictionaries, has an Eng-Eng dictionary and thesaurus, Oxford Collocations Dictionary, English Collocations Dictionary (unlike previous, also gives you Japanese translation), Japanese thesaurus, Super Daijirin (basically Japanese-Japanese), Katakana dictionary, Kanjigen (kanji lookup-- you can search by on/kun, stroke, radical, etc), and a word memo for words you want to save.
For me, it was a good 21000 Yen well spent (I got a discount, normally it would have ben 27000 or so). I'm happy with it. any more q's just pm me.