I've not successfully kexec'ed a 2.6 kernel yet (ok, I haven't successfully kexec'ed a 2.4 one either, but at least I get output with those.)
Oh, and kexec -f isn't the best way to use it - you're supposed to put kexec -e into /etc/init.d/reboot (just before the reboot command), load a kernel using kexec -l, then reboot normally. The kexec -e detects if a kernel has been loaded since the last reboot and starts it off, otherwise a normal reboot occurs.