As of now, raspbian packagespackage repo also contains raspberrypi-bootloader
package which contains firmware, kernel and kernel modules that rpi-update
downloads. The version is not the latest, but files should be fine and stable. Now it shows a 2013020720130902 version, so it's about 32 months old. The package is installed by default and is updated when a new version arrives in repo.
So you basically do not need rpi-update
if you don't want the bleeding edge firmware and kernel, just stick with apt-get
- it will update kernel, firmware and modules on its own. Actually I cannot find rpi-update
on my Pi at all.