My one recommendation would be to add the ability to use the user's email address in addition to their username as the 'username'.
Since we're using emailasusername plugin, we just use email address for normal login process.
Combining this plugin with a CDN (using a separate 'CDN for Joomla!' plugin) has proven to be quite effective in reducing our server load.
We've also had some issues with the default joomla caching before we tried this, for eg. the extended menu module was incorrectly cached. With the additional 'Global Exclude' option in jotcache, we were able resolve some issues with specific components/pages as well.
Good to see the plugin is being updated! This is definitely a very needed plugin if you have more than 10 people visiting your site :)
Hope to have some advanced options like how w3tc for wordpress has! At the least, I'd hope for alternate methods to save the cached pages, like apc or eaccelerator.
All in all, a great plugin & thanks for keeping it free!
My thanks to the developer