I'm not sure what all the grub2 changes are, but I do know that Grub2 is still experimental, and unless you're willing to risk a potentially dramatic failure (read as: all your systems become unbootable), you probably shouldn't play with it just yet. As far as hardware/software issues, Grub2 is meant to address items like running under more OSs and partitions, booting some of the more obscure hardware devices, and becoming smaller and more efficient. While you might need something like this, for your average computer user, Grub Legacy should work just fine.
Of course, you can decide for your self after reading the information on both programs at:
http://www.gnu.org/software/grub/
