PostgrtSQL instead of MySQL 4?

I've been running PostgreSQL with Coldfusion for about 6 years as well. You should note that the SQL in PostgreSQL is a bit more ANSI 99 complaint than other DB's and thus a bit different than MS SQL or MY SQL. Not much. Just a few little differences. One of my favorite O'reilly books is SQL in a Nutshell because it lays out the diffs in SQL from ANSI, MS SQL, MySQL,PostgreSQL and Oracle. It's nice to have on reference that covers all the flavors.

I always update the driver, but I'm also on Postgres 8.3.

You can get the most recent driver at:
http://jdbc.postgresql.org/

I also setup the datasource using the following:
Pick database type as "Other"
CF Data Source Name: whatever you want to use
JDBC URL: jdbc:postgresql://127.0.0.1:5432/dbname
(where 127.0.0.1 is the IP address of your postgresql server, 5432 is the port number that the server is listening on, and dbname is the name of the postgresql database you want to connect to)
Driver Class: org.postgresql.Driver
Driver Name: leave blank
User Name: name of PostgreSQL user that has access to desired database
Password: password of above PostgreSQL user

I've been using CF with PostgreSQL for about 6 years. Haven't had any problems like the ones outlined in the Null Pointer Exception thread.

Both MySQL and PostgreSQL will handily support an average use database-driven website. If you've been using nothing but MySQL, you would be well served to at least read up on PostgreSQL and find out if it meets your needs.