I have now tried "Power Favorites" and LinkMan. Both are nice tools but somehow don't manage to give me the comfortable feeling I had with powermarks. At least regarding LinkMan, which I still have on my PC, three things that frustrate me most are
1. No Automatic Suggestions while entering Tags. Here PowerMarks always used to suggest previously entered Tags, as one typed.
2. Folder Structure, instead of simple tag based structure. I guess, in LinkMan, one can choose to hide the folder pane. I personally, would like to see a folder panel, showing a tag based virtual folder structure, like in the not taking freeware WikidPad (http://wikidpad.python-hosting.com/
3. Duplicates & Marking the same site again: Both "Power Favorites", as well as LinkMan offer Duplicate Deletion. But PowerMarks simply did not have any duplicates. When one bookmarked a site which already existed in the database, PowerMarks very nicely opened the edit box for the preexisting bookmark, allowing one to make modifications if one wants to. This is much more flexible than a notice telling you that you already have that site bookmarked, and whether you would still like to mark it again (This, I guess is because of the hardcoded folder based approach).
I am sure that both LinkMan and Power Favorites will improve on their already impressive list of features, and hope that they incorporate features such as those mentioned above to approach the power and simplicity of powermarks. That will gain them many a customers like me, who are still crying over the demise of their favorite PowerMarks. :-)