[seanmcdirmid]

> Most students can fix grammar mistakes relatively easily once they notice them anyway.

You would be surprised! Especially with people whose first languages aren't English. Having something to provide feedback on grammar problems early on would be really useful. Of course, once they get grammar down, the next step is rhythm and flow, as well as reducing redundancy, and the biggest problem, as you say, is always the story, but you have to peel through lots of grammar problems before you get to that point. I edit a lot of research papers for my Chinese peers (most have PhDs, I work in a China-based research lab, so that isn't weird), so I'm pretty clear on the problems.