It would be nice to be able to add vocabulary to the spellchecker–proper nouns, specialized jargon, etc.
DT uses the standard Mac OS X spell checker.
Just feed in documents that have vocabulary you wish to add to the spelling dictionary, and invoke Check Spelling. Control click on each marked term and select Learn Spelling. A bit of manual work, but the terms will be remembered by Spell Checker next time it sees them.
…like a charm. Thank you very much.