I agree with the enhancement request approach if you want to change this. I don't myself see the justification for FALSE being a better default than true. I've never really seen the old behaviour as being very logical. Oracle knows that it can't use an index - but tries to use it anyway and errors. I can see that not using an index where you might expect Oracle to use one is something that people complain about in general, and I suppose there is an argument that my statement failing entirely is better than it taking longer than expected, but I don't really see either of those as justification for trying to do something that can't be done.
FYI, skip_unusable_indexes is now a pfile/spfile parameter in 10g (not only alter session based as in 8i/9i) and defaults to ... TRUE.
I would prefer FALSE as a better default value.
-- Niall Litchfield Oracle DBA http://www.orawin.info