People like to be entertained while learning. I have learned that my visitors like my site the best when I relax and talk to them on a personal level. Of course, I haven't thrown professionalism out the window. In reference to the tutorial, it is relaxed but in a professional sort of way, if you get my meaning. Relaxed style means a more friendly, one on one type of writing style.
Professionalism is clean, smooth reading material, error free and, well, professional.
I have come to the realization that to build a good community, which visitors want to come back to, both are needed. And yes, they can both exist quite happily, and, in fact, prosperously together. There are many ways you can implement personalization. It gives the personal touch. If you run a newsletter, you may want to consider having a section in it where you give your own opinions and ideas.