I think the writing is quite good, but maybe you could try adding a little bit more flare to the articles by reading up on some creative non-fiction techniques. I'm trying to learn how to write better myself, and sites like http://www.creativenonfiction.org/ seem to be a pretty good help.
There is also a book that I'm in the midst of reading called "Writing Creative Non-fiction" (ISBN 1-88491-050-5), and I find it very helpful. I also think the book "Eats, Shoots & Leaves" is a great book on punctuation, though I don't think you have a problem with that.
Anyways, you write a lot better than I do, and I think that you're articles are professional for the most part. I just think that the articles are missing a unique 'writing style', if you know what I mean.