I upgraded from F14 to F15 using yum, via the instructions on the wiki.

After the upgrade, grub doesn't let me interrupt to select a non-default kernel. I.e., when it says what kernel it's going to boot and is counting down, it won't interrupt the countdown and give me a menu regardless of what key I hit.

Here's my grub.conf:

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/mapper/vg_jik2-lv_root
#          initrd /initrd-[generic-]version.img
#boot=/dev/sda
default=0
timeout=8
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
# rhgb quiet
title Fedora (2.6.38.8-32.fc15.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.38.8-32.fc15.x86_64 ro root=/dev/mapper/vg_jik2-lv_root noiswmd LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us
	initrd /initramfs-2.6.38.8-32.fc15.x86_64.img
title Fedora (2.6.35.13-92.fc14.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.35.13-92.fc14.x86_64 ro root=/dev/mapper/vg_jik2-lv_root noiswmd LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us
	initrd /initramfs-2.6.35.13-92.fc14.x86_64.img
title Fedora (2.6.35.13-91.fc14.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.35.13-91.fc14.x86_64 ro root=/dev/mapper/vg_jik2-lv_root noiswmd LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us
	initrd /initramfs-2.6.35.13-91.fc14.x86_64.img