Popular social bookmarking service del.icio.us has finally unveiled one of its most significant and anticipated redesigns since launching in 2003. Ars Technica went hands on to see what Yahoo has in store for the next generation of social bookmarking.

As a quick primer for those who haven't hopped on the bandwagon yet: social bookmarking websites allow you to save URLs in "the cloud" instead of in a single browser. Bookmarks can be tagged with multiple keywords for easy categorization and recall, which offers a number of benefits. First, sites like these are great resources for watching what other human beings (not automated search engines) are interested in. Second, by harnessing the many integrated tools for both saving and retrieving bookmarks, you can harness these social filtering tools as a way to liberate your web browsing habits since your bookmarks are no longer locked up in a single browser or even computer.

One of the most subtle, yet important, changes in the new Delicious (called "delicious 2" by everyone but its developers) is the loss of two periods from its name. The URL used for the service until now has always been a clever play on domain names: del.icio.us. Now that URL, and all links to bookmarks saved at it, redirect to the much friendlier delicious.com.

Explained in an announcement blog post, the new Delicious focuses on three fundamentals: speed, search, and design. Browsing through the site, that first criterion has clearly been met. Yahoo says Delicious has over 5 million users now, and as a regular user of the site for around three years, I've noticed the gradual slowdown that Delicious acknowledges. That creeping sluggishness is nowhere to be found anymore, though, and clicking through tags from both my own bookmarks and across the site's community is really zippy.

Next on Delicious' menu is the all-important search, which again focused on speed but also utility. I no longer have time to make a pot of coffee while waiting for results, and Delicious' search is both more accurate and social. A search can be directed at one's own tags, a single user's public bookmarks, the bookmarks from one's social network, or of course, the entirety of Delicious. Either way, searches are lightning quick, though I'm disappointed to see the default search option point at the entirety of Delicious, instead of my own bookmarks. Perhaps the Delicious crew has real user statistics to prove that this is the better choice, but I prefer rooting through my own maze of bookmarks and tags before embarking out through the rest of Delicious. At the least, I would like a feature to customize this default setting.

As a brief side note, I'm very glad to see that the Delicious crew maintained composure when it comes to the social networking aspects of the site. The ability to add friends and send links to other users is definitely a value of the service. But in the back of my mind I always worried that this new version would bring a lot of ridiculous cruft like extensive user profiles or, heck, even minigames like "Link that beer" or "URL Scrabble." It's refreshing to see that the site maintained just the bare necessities of a "network" list of friends, as well as "fans" who are interested in what you're bookmarking.

Easily the most significant change to the new Delicious is the team's third criteria: design. Yahoo says that improving usability and adding a handful of frequently requested features were top priorities, and it shows. Delicious' UI is much cleaner now, with bookmark metadata like dates and tags getting cleaned up with more relevant placement and visual markup. A new colorized counter accompanies each bookmark to let the user know how many others have saved the same URL, and the light blue color gets darker and heavier as that number increases.

A handful of new tools have been added to the site to make it easier to navigate bookmarks and hone in on a specific tag. In the top left of each bookmark list, for example, are three view buttons that allow for adjusting how much metadata is displayed with each bookmark (tags, URL, etc.). Bookmarks can now be sorted alphabetically in addition to chronologically, and a "Top 10 Tags" widget in the right sidebar of each user page offers a quick glimpse at what kinds of bookmarks make him or her tick. Lots of smaller bits of polish sprinkled throughout make the new design a joy to explore. Check out a clever video the Delicious team put together that does a great job of highlighting the feature evolution this update brings:

With all of these welcome changes, though, Delicious still suffers from some rough edges and bizarre stubbornness. One previously existing feature that allows for automatic blogging of the day's bookmarks, for example, is still listed as "experimental" and is fairly clunky to set up.

On a grander scale, Delicious is sticking with its single-word philosophy for tagging bookmarks on the service, instead of adopting the far more useful comma-separated method that most other sites have agreed on. This means that if you add 'Mac OS X' as a tag to a bookmark, you've actually added three tags: "Mac," "OS," and "X." This needlessly restrictive limitation can make the process of building a tag hierarchy frustrating, especially for new users.

That said, the new Delicious is largely a success. The new design is far easier to navigate and provides a lot of useful ways to visualize bookmarks from one's own collection and across the site. The speed brings a refreshing boost to performance for those who frequent the site, and some limited testing shows that existing clients for posting and retrieving bookmarks still work perfectly well. The new Delicious may not bring a revolutionary change to social bookmarking, but the significant changes are a very welcome evolution.