I always used a narrow and they'd all just start chasing me. I never tried Demon Souls, picked up a Splinter Cell game today and dude that worked at DS saw I bought the CE of DS2 and was shocked when I told him I never tried Demon Souls.
I probably should have downloaded it when it was free.
Just always download everything on PS Plus. Every month, download everything. If you don't really want it, just immediatly skip the download, it will still register as a bought game and you will be able to redownload it anytime you want