rtree, btree, hash index methods...should I care?

Hi Folks,

First let me just say that I am very positive about Postgres. I am
using it in conjunction with the AOLserver web server and am really glad
that it is so stable. It stays up for weeks at a time. I have never
had a crash or any data corruption.

Actual question:

Do I need to care about rtree/btree/hash methods? Is there a
performance difference in "normal" operations? What about when using 3
or 4 JOINs together?

Obviously the hash index is only useful for equals; and btree does seem
useful.

How much more of a "cost" is there in terms of inserts and updates if I
make 2 indexes (one btree, one rtree) on the same table?

./patrick