Once Bitcoin trickles into more Linux distributions, I think one great advantage will be the fact, that a payment system is just one "apt-get install" away. Just install some software packages and you are ready to receive and send Bitcoins. Think LAMPB: Linux, Apache, MySql, PHP and Bitcoin. :-)

I'm wondering what a good standard setup for this would be. Linux distributions could integrate the necessary daemon scripts to run bitcoind as a system service to which you then connect using the JSON-RPC interface. But maybe bitcoind should support some kind of user schema for that? In the same way that you only run one instance of mysqld, but can have different user accounts using databases that are isolated from each other. There would be only one bitcoind running and only one copy of the block chain be managed, but several different wallets that can be accessed by supplying different user credentials using the JSON-RPC interface.

Do you feel that this is something that should be added to bitcoind at some point? or would you prefer this to be an external component that provides the user management on top of a single wallet?

Until Bitcoin gets user functionality, I think it'd be best for each user to run his own instance of Bitcoin running with "-connect=127.0.0.1 -nolisten" to connect to the one network-facing process.