I've been using Digg [TechCrunch][Sourcelabs] for a while now, it's a great way to find out what's new and interesting out there and is an alternative to having lots of RSSs agregated in Google Reader or the like.

I like the fact when you register it has the "recommend a friend" option where you can virally promote the service to your IT buddies. I will definately add this feature on my pet site as it's a great way to get the word around, especially in a sports based arena with team mates.

It would be nice if they did something similar to google reader and allow you to publish your 'dugg' sites on your own site.You can view what I've dugg here and it actually allows you to view by category as well.
Actually, with the RSS feed, you could do this feature with a bit of work although the RSS is for all your dugg's rather than being able to dig down into each category.

You can even have links to allow people to digg your articles too by just simply adding a link.
Also, in the profile section, they don't have skype as a IM client which is a bit odd!

The Digg spy page is pretty impressive with realtime action of what's going on!