In my opinon the great disadvantage of MS thesaurus implementaion is that sql server does not use forms of thesaurus words.
If user wants to have "full functional synonym" he should add expansion for all forms of words.
Tabke contains records with forms of word "source", I added synonyms
In this case if I search word "rivers" or "drank" I never find these records(!).
But if I added yet expansion:
In this case I search "drank" and I can find records with "source".