My needs are basically an auto-tagging feature. Simple Tags wasn’t working for me in this respect: I tend to post lengthy articles, and clicking for suggestions from Yahoo or TagTheNet always results in “no results.” For shorter articles, the suggestion feature seems to work fine.
So I downloaded Tagaroo, which gave me great suggestions from Calais and had the added bonus of finding related pictures on Flikr. So far so good, except that when I choose from the suggested Tagaroo tags and save the post, it doesn’t add the tags.
I thought that maybe Tagaroo was trying to populate the original WP tags field, which Simple Tags had replaced with it’s own (admittedly improved) tag field. So I deactivated simple tags, but the original WP tags field did NOT reappear!