Disqus over the default commenting engine, what are some pros and cons?

As subjective as this question might sound, pros and cons in the technical sense is what I’m looking for as answers.

I’ve been using WordPress for about 2-3 weeks and 9/10 of the comments are spam, so I’m think it would be a lot better if I use a disqus because it’s “more social” in the sense that it connects Facebook and Twitter accounts in it as well and I’m looking for a more cleaner interface.

Am I thinking in the correct way? Am I missing something and should I stick with the default commenting engine? Please do give a reason or explanation for why you believe one is useful over the other.

Also, what’s Disqus’ situation with the spam situation? Can I get some links to real WP blogs/sites with disqus running?

Edit: Does disqus have a spam filter?

You asked specifically about disqus, and as this is somewhat subjective even for technical answers (only because some answers are of technical nature, it does not mean they are not subjective), it’s probably worth to look a bit around what others have asked and answered: What is the best method for handling comments?

You can however just opt-in with disqus. At startup, it will sync the existing comments of your blog. Then, new comments on disqus will get synched with your blog as well. So you can just try and if it pleases you and your users, you stick to it, otherwise drop it. You won’t loose any of your comments (disqus for wordpress, needs signup).