just re-flashed my device yesterday, and apart from the default repository i have only enabled Extra's. As i installed each app im monitoring rootfs space, and if after an app install's a significant amount is used i do an apt-get clean and reboot.
I've noticed 2 app's so far in the Extra repository out of around 10 i've installed are taking a bit of limited rootfs space.

touch search (2.1-2) 2mb
extra decoders support (0.3.4-1) 3mb

could someone more knowledgeable test this , as i build my N900 up to where it was pre flash i've add more app's from extra's, testing and dev i expect them to use rootfs.