Two things I have noticed, the latter of which is more important:
1) Remove the inline styles.
You should use wp_head() to add a separate stylesheet in, specifically targeted to form fields using Grunion. Preferably, you could also add a setting in a control panel page that gives users the option to disable the loading of your styles. Not everyone is a fan of Lucida Grande.
2) Support line breaks in the Feedbacks view.
I'm using Grunion to run an article submission form for a student magazine. I just realized that line breaks aren't showing up under the Feedback view, which is crucial. Entire poems with different stanzas come out as one big paragraph. They're formatted right in the admin emails, though.
Thanks for continuing to develop Grunion, but I would appreciate it if these problems are fixed.