Have a look at that thread I mentioned, especially pages 22 & 23 where the package in 'testing' is discussed. The OP and pricipal Maemo-CUPS dev, Mase, gave me some tips. If you're not sure about something, specific to the package itself, he (?) would probably respond to that thread.

Re: mp-fremantle-generic-pr: There is no info about this on its package page but from what a power-search reveals, it seems to be a hook for the OS updater to use. However, where core OS updates are concerned, reflashing to new versions should still be possible and back-ups are still required/advised whether OTA or flashed. Is there something I'm missing?
Just has a look through some TMO and bugzilla items for this package. Have a look through bug 11831 to see if that shed any light on the matter. Also, this page should set you at ease.

I have installed the CUPS packages in the Maemo repositories with no notable problems (not running CSSU yet). I have not tested it yet because I need to treat myself to a usb OTG cable. When I do I'll be doing my best to get direct printing from my N900 fully funtional.
- Why? Well, the device is always on so rather than faff around transfering files to another computer, which may need to be started up, why not output directly from the N900 itself, it's not as though it can't be done?