Also if anyone misses the “More…” button, you can re-enable it by editing the plugin and adding the following line before line #145 (which reads “echo $after_widget;”)
echo '<a href="' . get_category_link($instance["cat"]) . '">More...</a>';
A warning that the widgets would need to be rebuilt would have been great, but a migration of the existing wp-options entry would have been better. I realize that this is a free plugin but at over 250K downloads these changes affect a ton of sites.
@biranit: Thanks for the quick and easy solutions! I’m also hoping that the stylesheet is optional in the future.