My Take
I really like Pixton for a few reasons. It is a few clicks of the mouse to set up a class account, and it is very simple for the students to join our class. I also love that they technically don't need to share anything with me since I can view all of my students' works in my class account.
My students were able to fly through creating comics with these. Because the interface is pretty user-friendly, they could focus most on content which is what is important to me. Students have a lot of creative license with this tool.
This isn't the greatest tool for students who need extra support, however. There are so many options that these students can get lost easily and sometimes aren't sure where to begin.
How I Use It
This can be used for all subject-areas, just as you would use any storytelling tool. I think it would be too overwhelming for elementary students, but it works well for my K-12 students world languages students (Spanish). This would fit in nicely in an ESL class as well.
We used this in Spanish I as a project to end our introductory conversation unit. Students enjoy picking the backgrounds, characters and layouts, and these pieces inspire them to be creative with the dialogue that they input.
At first, we tried to use this website on our ipads. The ipads don't support flash, however, so I needed to re-arrange to get ahold of laptops instead. I recommend that teachers take care of restrictive pop-up blockers and out-of-date flash players on their computers before they start using this tool.
I use the free trial class account which students can join with the invitation code that Pixton provides the teacher with. This made things streamlined for us. I can view progress of any student's comic through the teacher portal of our class account.