I just feel that requiring an opening tag no longer makes sense. PHP has matured beyond dynamic web pages, and is used more and more for full web applications. PHP still makes the assumptions of a templating engine. It's almost like PHP needs two modes, an application/scripting mode, and a template mode (like Ruby's ERB). In your apache configuration, you could apply the template mode to all files of a particular extension, e.g. phpt. Within php itself, to load a template, you should have to use something other than require() or include(), such as template() or render(). A method such as template() or render() would return the output, rather than send it straight back to the browser. Then you wouldn't need to capture the output using output buffer functions.
In application mode, mod_php could add extra smarts, such as forking the parsed PHP program for every request, or instantiate a new application object for each request, instead of re-parsing everything - this behaviour should be out of the box, you shouldn't need 3rd party extensions to achieve this.
By the way, I'm not switching from Ruby. PHP just looked like a more suitable option for a simple file based CMS I have in mind (and no, it's not like any other CMS currently out there), though on further investigation, PHP's lack of a single-point of entry makes this a little more difficult (this goes back to having an application mode in mod_php).
PHP has a couple of things going for it. First, it's a template engine out of the box. You don't want to throw this away, as it's why PHP become popular, and it's still very useful. The other thing is that PHP provides traditional object-orientated constructs, such as Classes, Interfaces, Traits, etc, while still being a dynamic language. I'm sure for all the major PHP, it's the traditional and familiar language constructs that probably make PHP so popular among more serious programmers. I say all this because people often fear that changing PHP too much will have it lose the things unique to it, but that's not true if the changes you make are thoughtful.