Christopher Hester (Designdetector) was impressed by Opera's bookmark search:
In Firefox, the search only looks for matches in the title of the bookmark. So if a page about Firefox was stored as "Exciting New Browser" it won't find the link. However, Opera also looks in the address, keyword (called "nickname" in Opera) and description of each bookmark. (And it's blazingly fast at searching too.)
future of bookmarks may already be here…
Here is an article: The Future Of Bookmarks.
Yes- it is a very cool feature of opera. I though all kinds of metadata in to the description of the bookmark. Whatever I’m thinking at the time I bookmark usually goes there.