Can you provide more information? I’m the developer of this plug-in and haven’t heard any reports of problems yet. I just double-checked that this works on a fresh 3.1 install and had no problems (even with the new advanced ‘screen options’ form!) (lucky me!).
You may have misunderstood what the plugin does?
This doesn’t hide existing comments. It simply disables the page comments check-boxes as a default option. This plugin is for people using wordpress as a CMS who use lots of pages, rather than posts. For these users, unchecking the “show page comments” and “allow track backs /pingbacks” form on every new page is a chore. This plugin is designed to help with that tiny nuisance.
If you are having problems with the plugins functionality, please provide more information. (WordPress version, steps you followed, what you expected, and what happened) Thank you.