Tim Bray is right on with this (and welcome back to North America, Tim!).
People don't want to have to muck around with 15 fields and widgets in a search form. How on earth would I know if the term I'm looking for is in the Title, Creator, Description, URL, whatever field? Unless I already knew what I was looking for, in which case I probably wouldn't be using a search engine...
We need to build Simple Search (i.e., a single text field with a "Go" button) to be smart enough that it's all that is required. I can't remember the last time I used the Advanced Search form in CAREO, aside from testing/debugging the form itself.
Which would you be more likely to use?
I wouldn't be at all surprised if APOLLO didn't even have an "advanced search" form (unless the users scream for one, that is).