I dont tried to use grub because, I have some surprises in older
versions of conectiva.
Then I always use lilo in all distribution that I have installed.
The last version of lilo presents a graphical screen and works well
One thing to take care is that after upgrade the kernel, you have to
make a little edit in /etc/lilo.conf and the execute lilo
The edition is to put the correct path to the kernel file.
If you use ( or apt-get make it inconditionally ) rpm -U
you could have problems to do the next boot.
Use rpm -i to preserve the old kernel file, In case of an
accidental reboot withou edit /etc/lilo.conf
In this situations, I dont know what must be done or edited
in case of Grub, then I dont use it ( for a while ... )