It is slightly worse than Delicious. Haven't used the other two. It is disappointing that Google gets the remarkably simple things wrong and then adds convoluted features that don't appear to be useful to most users.

Two annoying things I remember:

The front page is always sorted by title. When is that ever useful? I want to see my recent bookmarks without having to resort.

When you search within Bookmarks it pulls in "social" results from complete strangers you haven't bookmarked or asked for. You have to select "My Bookmarks" after the search to redo it.

Never used the hyped "list" feature, don't really know what it is for.

If you keep private bookmarks it is fine. There is no useful front page of popular public tagged bookmarks like Delicious has.

Bookmarked pages show up in related search results which is useful.

Google Bookmarks seem private by default, unlike Delicious and Pinboard; seems like you have to put bookmarks into "lists" to make them public.

I've just started poking around again, and the first thing that stands out to me is that the URLs are long and complicated. Delicious and Pinboard both put an emphasis on readable, hackable URLs, which makes sense for this type of pretty-much-a-database service.

Pinboard is better.

Use Firefox with Slurp and keep your bookmarks to yourself. Delicious experiment shows that your bookmarks are not worth anything to anyone but yourself.