I'm using wordpress 3.5.2, which is most current. I'm wondering if your plugin has been tested with that.
I'm using the "after the deadline" plugin for both ff and chrome. Any conflicts. (Actually, I wonder if your plugin would simply replace ATD. I only use it for blogging anyway.)
Any known conflicts with Joost WordPress SEO. That has some level grammar checking in it too.
Finally, are there any screenshots to go with the plugin?
What you've done sounds great. Its something that would really help me a lot.
I'm looking forward to trying your plugin, but have these few concerns.
P.S. If I can make one suggestion: it would be nice if your plugin included the flesch kincaid reading score and/or grade level. I tend to write long sentences and I use that score to keep my writing in check.