Using the internal data dictionary

I need to assemble a complete data dictionary for project documentation and other purposes and I was wondering about the pros and cons of using the pg_catalog metadata. But I hesitate to poke around in here because I don't know why it's kept so out of sight and not much documented. But it seems like an ideal source of information to tap with a program to generate accurate, current reports of what's in the database.

Is this a bad idea (everything I'm thinking of doing would be read only except for the description fields) but I'd just like to make sure that there's not some innocent looking table in there that acts as a doomsday device if you so much as read its first record, etc. I'm just not sure why this isn't more widely used or talked about.

Regards,

Bill Thoen
GISnet
http://gisnet.com
303-786-9961