My blogs are both set up to moderate the first comment, and then allow any subsequent comments.
I'd tweak it a little ... make it so that it requires more posts (say 3, 5 or 10) and make dofollow. Then with users that you can tell are legit good quality, flip the switch after the first post or as you deem as appropriate. Using your experiences here at the forum, I don't frequently need to check your posts cuz I have a feel that you are not going to be spamming the forum but I sure am familiar with them as I naturally read them as i participate in the conversation myself. I'd take a similar approach with your blog. It influenced you here, and I believe you'd have similar experiences with your blog ... with time. There is no issue with dofollow if quality content, and imo an advantage.