Get an ipod touch, then buy Japanese (
http://www.codefromtokyo.com/japanese). It's pretty much replaced every other dictionary I own, paper or electronic. It uses the Jim Breen database (but doesn't need wifi connection), allows kanji lookup by writing it on the screen (if you turn on chinese handwriting input) or by radical, allows you to compile your own vocab lists, contains lists of proverbs, counters, allows you to view entries/kanji by radical/stroke count/school year or JLPT level AND gives you a countdown to the next JLPT test. Best dictionary ever.