On a first glance, it may sound like a "nice toy" - which it is, in fact. But it's much more! It's the answer to Google Tooltips - the "translate word under cursor" feature shipping with the Google toolbar. And it does not interfere with it (the Google tip always opens right-hand under the cursor, and you can configure the Hebrew tooltip to open left on top of the cursor). Giving you a list of translations by types (noun, verbs, etc.), it gets back the vocabulary from the Cheder (or the Hebrew study at university) to your brain. Nice and useful, including learning effect.

Not the most functional and featured tool, but does a great job for what it is (a JavaScript engine).
I really hope that very soon Midori's and Epiphany's User-script Managers will support the full API of Greasemonkey.
I hate FireFox/ThunderBird and XUL :P (seriously).