I have not kept up with PostgreSQL changes and have just been using it. A co-worker recently told me that you need to word "CONCURRENTLY" in "CREATE INDEX" to avoid table locking. I called BS on this because to my knowledge PostgreSQL does not lock tables. I referenced this page in the documentation:
However, I do see this sentece in the indexing page that was not in the docs prior to 8.0:
"Creating an index can interfere with regular operation of a database. Normally PostgreSQL locks the table to be indexed against writes and performs the entire index build with a single scan of the table."