Brooklyn BloggEd Manila is a very powerful tool but it's not for everyone. Lots of teachers won't take the time to learn it in anything close to its current form. Simply put, it's more than most teachers need and the learning curve for a teacher not fascinated by technology is too steep.
Joe makes a point that Manila may be too difficult for the average teacher to use as a web publishing tool. I have used Manila for over 2 years. When it was first pointed out to me by Dick McPartland of Lincoln High School in Portland, I was taken by its ease of use. It allowed folks not familiar with web publishing and web methods to upload content. We utilized it with our Teachers on Special Assigntment (Curriculum Specialists) to allow them to post information about their particular curriculum area on the web.
While much easier than traditional web posting methods, I found that the interface was not as intuitive as I first thought. For example the seperation of Stories and News Items was confusing for some of our folks. If they wanted to make a post about an upcoming workshop, they would first have to create the story and then the news item that pointed to the story. While this did not seem like such a problem to me, time and time again the content people found it confusing. Movable Type makes this much easier with the Extended Entry field. No need for a seperate story and a seperate news post about the story.
The uploading of images is another area where I find Movable Type to be more intuitive. The ability to upload the image, create a thumbnail, and then edit a post to go with the image is another example of why I like Movable Type.
Nothing against Manila, but I'm finding for my work at Buckman, Movable Type is a better choice.