What is so great about Wikitionary? ATM, nothing much. Project spawned off Wikipedia in Dec 2002 is new and defiently 'work in progress'. Much of the entries I check didn't exist (i.e. didn't exist before I added them ;). But the potential...imagining entering ANY word, and getting its: etymology, definition, grammar notes, pronouciation, quotatons, synonyms, antonyms, derived and related terms and last but not least translation into all existing languages (including conlangs).
Breathtaking vision? Sure! :)