rheathers, the mobile toggle should still be there, but it’s JavaScript ‘powered’ now instead of CSS3. Please could you post a link to your site? You might have a JavaScript error on your page.
Becky, the CSS should be automatically regenerated when you update the plugin, it’s a pain to actually test though (I haven’t figured out a way to simulate the plugin update process locally). In theory it should work but I’ll double check that. But yes, saving a theme, or the menu, or the settings will regenerate the CSS for you.
Sorry for the hassle of having to redo the CSS, I don’t make changes like this lightly… the problem with the CSS approach before was it relied on the menu ID’s being unique (as they should be), but themes have a habit of outputting the exact same menu twice (resulting in duplicate IDs, and therefore breaking the toggle button) – resulting in lots of support and the button not working ‘out of the box’. The JavaScript approach thats in place now should work even with duplicate IDs and hopefully it will make it easier for people to get up and running in the future.