bitmap indexes - performance

Using as a starting point the old bitmap patch in:

http://archives.postgresql.org/message-id/20081101000154.GO27872@fune

I re-applied and re-worked the patch to see what kind of improvements over
btrees bitmaps actually provided.

Using a 20M rows table of 10/100/1000 random values, I've found that:

1) bulk index creation time is roughly 6 times better
2) index size is 6-15 times smaller (depending on column cardinality)
3) there's almost no difference in query times (but I have to make more
tests)
4) I can't say anything about the insertion performance, but I guess
bitmap will perform way worse than btree

Are these improvements (index creation time, index size) worth enough
to keep on working on this?

I mean: given that bitmaps don't give any benefits in query times, but
only benefits related to disk size and bulk index creation times, and
will have horrible performance for insertions/deletions: would this job be
worthed?

In case it is: I will try to clean up the patch and post it...

As a side note: I guess that most of the bitmap indexes performance
improvements in the SELECT area are already implemented in postgres
in the bitmapand/or and bitmap scan stuff? I couldn't find any docs that
say that bitmap indexes are faster for selects, unless of course they
are ANDed/ORed together (which is something postgres already does
for regular btree indexes)