I used LinkStash for a long time, but gave it up after realizing that I just am not able to make use of the folder based structure. Then I shifted to PowerMarks and the simplicity, + power + tag based structure made me fall in love with it.
However now that PowerMarks will not be updated, and will never have a portable version. I am once again on the lookout for an alternative.
miTaggedMarks came the closest, with a powermarks import utility, and a portable version, but is much more troublesome to use than PowerMarks, especially when it comes to entering tags.
The new LinkStash 2 is much better with a good tag & search system, but I do not understand why it does not allow one to update the existing bookmark, if one tries to enter a pre-existing address again, instead of giving a very inflexible "duplicated bookmark" warning.
"Portable Bookmarks" looks nice but does not have the possibility to enter longer description/notes as is the case with the above two programs.
I do wish that someone revives PowerMarks or that LinkStash lets one simply update existing bookmarks instead of shouting about duplication.