Old grub legacy seemed to work from partitions, but grub2 is larger to accommodate many new features and uses block lists which are hard coded addresses to find the rest of grub instead of file names. When grub is updated it may move on the drive and you will have to reinstall grub to the partition to fix it. That is why it is less reliable, but it will work.
With 9.04, I used chain loading for everything and with 9.10 I installed grub2 to its partition. It worked as I was able to chain load and I had it that way for a while, but I do not think there were any updates. I then converted to grub2 in the MBR and now like grub2.
If you are using Fedora to boot and its current grub legacy then you should just be able to add a boot stanza in Fedora's grub.conf. Fedora's new alpha uses grub2.
Set X to drive number 0 or 1 that Fedora sees it as. And Y to grub legacy number of partition. Chainload only works if grub is installed to partition.
title Ubuntu 11.04
title Ubuntu 9.04 Jaunty 64 bit @ sdc5
title Most Current Ubuntu on sdc5
kernel /vmlinuz root=/dev/sdc5 ro quiet splash