i use wordpress for all may blog sites. it’s very popular software, used by lot’s of “important” bloggers.
But like prof said, it’s buggy. It’s slow, it’s insecure, the password for the database connection is kept in the live website root directory, etc. There was an “injection bug” that someone used to hack and mess up my site.
but you can’t beat the price and the amount knowledge available on boards, etc. for using/maintaining it.