I've started back up Demon's Souls myself. Love the shit out of Dark Souls, but the PC version is kind of a hassle to get working and I just don't feel like doing it when I have Demon's laying around. I think the only thing I really disliked as a change from Demon's Souls to Dark Souls is I much prefer the Nexus hub rather than the busywork of getting to and from each location, pre-warp. The monster design for bosses I think was also a bit better in Demon's, but so many other things were improvements in Dark that I can't complain too much about it.