I've already updated the MetaTitle plugin. Andy at Digging in a Habari sandpit asked that it have the option of working even if the theme's template doesn't have an html title tag. I added this option to MetaTitle. The theme does still need to have an html head tag, though. To be honest, if it doesn't you really need to add it or use a different theme because the theme you're using is screwed up.
While I was at it, I added the ability to give posts and static pages a different html title than the post's or page's actual title. This was implemented by adding controls to the publish page for entries and pages. It can come in handy to create an html title that is better optimized for SEO purposes, or to give a more descriptive title to static pages that have a short title to allow them to fit in menus properly.
You can download the updated plugin from the Plugins page.
As always, enjoy! If you have any questions, problems, or feature requests, let me know.