I think comments is a must. Interacting with your readers will help you improve your self. Having their comments and feedbacks will determine if they truly understand what you write. Besides, you are doing it for them to read. Let them share their own thoughts and maybe you will get some ideas from them. Regarding about the spam, there are many plugins that prevent it nowadays. That is why don’t worry about them.
If you want a blog that is alive with more traffic and better interaction, then comment section is for you.
Making it dofollow could also get you some backlinks; you know those “dofollow blogs” lists?.. 
Having comments is not useful at all, it is just a way to know that people like your articles. However if it’s spam comments… -_-’
I saw a very good website about tutorial, deisgns, ect, it has PR 5 but very very few comments (some of the articles have only 5 comments) but the content was really great!
If you want to have more comments, make your blog dofollow.
I put my blog in dofollow yesterday and today i receive many comments but more than 50% of them are spam and completely out of the suject of the article.
Then Your should put a spam comment catcher. like akismet.
Yeah, it is what i do after deleting all these spams.