Of all the Japanese dictionary programs that use the JEDict database, Tensai has far and away the best balance of speed, features and design.

The keyboard shortcuts added to the latest version make looking up words in Tensai almost as quick as thought. It's so quick and easy that, while chatting with people in my office, I can look up words in mid-sentence without interrupting the flow of the conversation at all. It's like a hyperboost for my brain.

The system-wide "Look up in Tensai" service is solid gold: select a Japanese word in any program anywhere, press command-shift-T, and Tensai pops up and displays your results. Reading newspapers, academic journals, encyclopedia articles--anything digital--it's a snap thanks to Tensai. The psychological resistance and fatigue normally encountered while reading Japanese are all but annihilated. I can read anything, heiki, thanks to Tensai.

The only place where Tensai comes up short compared to the main contender, the JEDict program, is its lack of JEDict's incredible Kanji component lookup feature. Unfortunately, JEDict's interface is so cluttered, counterintuitive, redundant and inconsistent that this feature is thoroughly not worth the trouble, especially since the occasions on which this feature might have saved you a few seconds become fewer and fewer the more Kanji you know. You're better off to just count the strokes and use the Character Palette.