I'd recommend this dictionary to any starting student in Japanese. The entries are in Romaji, so looking up colloquialisms is no problem. Plenty of illustrations of usage are included under each entry, and it's a rare occasion when I can't find what I'm looking for.
Of course, it's no subsitute for a kanji dictionary, but one of the burdens that students must bear in learning Japanese is that they will eventually need at least two Japanese-English dictionaries - one for looking up words they hear and another for kanji. If you select this dictionary for the first category you won't go wrong.