System (Hidden) Keys

We are about to have a massive debate in the company I work with. The discussion will be about primary keys that are system generated, (like by a sequence) vs. a set of 'regular' fields that can be used as unique primary keys.

What I'm looking for is basically a list of PROs and CONs about defining Primary keys in these two ways.

For example, it has been stated that there is Overhead required to store a system primary key that the user never sees.

Also, the Where clauses of most queries will be simpler if a single Primary key field can be used...

etc.
Anyone ever go through this process before? (I mean 'proving' a design philosophy to a group by citing this kind of PRO CON list specifically on this topic? )

Just fishin'
I'll summarize any responses.
Thanks
Randy

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