Shouldn't have any trouble as long as you install Win2k8 last (otherwise XP will overwrite the BCD bootloader with the old-style NTLDR; you can still restore the BCD loader afterwards but it's just easier if you do it the right
way around to begin with).
Why not just install Win2k8 in a VM though? Saves you having to reboot when you want to experiment with it.
Performance, primarily. 2k8 is slow as crap in a VM (since I can't allocate all my RAM to it, it has to swap constantly... I've got 1 GiB, but
I can only allocate 512 GiB to the VM).