Another Mod you can do. Instead of network shares and blah blah.

Setup ssh server on the n900.
Then on a linux machine. You can make a launcher whose command is.

This will open up a folder to the folders which you would get via Mass Media mode. Except this doesnt have to be connected to anything when you're doing it. You also dont lose all your files access. Though performance wise. It'll be far worse. If you have any video going or something it'll be laggy when you transfer. Also the Wireless G speed is far slower then USB 2.0. Literally 10x faster if you use usb.

Simple option if you dont want to do any sort of kernel mod or whatever.