Huh, You released 5.3 and even does not check this bug report. You FAIL

I'm having the exact same issue. PHP 5.4.7. The Namespace is never imported and 
can only be used when referencing the full or partial namespace path. This isn't 
close enough to how the expected functionality would work. This makes partially 
useless because all existing code that didn't call namespaces directly with 
their full or partial path referencing classes/methods etc wont work. You can't 
simply wrap your classes in a namespace and have them encapsulated for easy 
import where appropriate. 

Errant code:
--------------------
<?php
namespace Minnow\Framework{
	class Startup{
		public static function launchApplication(){
			echo 'Application launched';
		}
	}
}

namespace WebRoot{
	use Minnow\Framework;
	Startup::launchApplication();
}

Fatal error: Class 'WebRoot\Startup' not found in 
/Users/jeffreytgilbert/Desktop/Namespace-test-failure-use-namespace.php.php on 
line 12


Errant code: 
---------------------

<?php
namespace Minnow\Framework{
	class Startup{
		public static function launchApplication(){
			echo 'Application launched';
		}
	}
}

namespace WebRoot{
	use Minnow\Framework;
	\Startup::launchApplication();
}


Fatal error: Class 'Startup' not found in 
/Users/jeffreytgilbert/Desktop/Namepsace-test-failure-root-namespace.php on line 
12



Errant code:

<?php
namespace Minnow\Framework{
	class Startup{
		public static function launchApplication(){
			echo 'Application launched';
		}
	}
}

namespace WebRoot{
	use Minnow\Framework;
	Startup::launchApplication();
}



Fatal error: Class 'WebRoot\Startup' not found in 
/Users/jeffreytgilbert/Desktop/Namespace-test-default-namespace.php on line 12


=====================================
-- this is the part that chafes me
=====================================

<?php
namespace Minnow\Framework{
	class Startup{
		public static function launchApplication(){
			echo 'Application launched';
		}
	}
}

namespace WebRoot{
	\Minnow\Framework\Startup::launchApplication();
}

Works fine, which is silly because then it makes the "use" arguments pointless 
because this still works, which it should, but doesnt work in the global or 
default scope. 

<?php
namespace Minnow\Framework{
	class Startup{
		public static function launchApplication(){
			echo 'Application launched';
		}
	}
}

namespace WebRoot{
	use Minnow\Framework;
	\Minnow\Framework\Startup::launchApplication();
}

Indeed, implicitly importing all symbols of a namespace as can be
done in Java with

  import mynamespace.*;
  
is not implemented in PHP. This would require the RFC process[1],
though, so I'm suspending this ticket.

[1] <https://wiki.php.net/rfc/howto>

1. (re: OP) That code is impossible because whichHand() would be ambiguous: is it calling the function from Utils\Left or from Utils\Right? Aliasing is not a runtime operation that "updates" the local symbol table or something similar - it is used to resolve names at compile-time.

2. (re: @jeffreytgilbert) "use" is not an namespace import. You "use" an individual class. "use Minnow\Framework\Startup" and "Startup::launchApplication()" is the solution.

3. Functions can be use-d as of PHP 5.6.
https://wiki.php.net/rfc/use_function
https://3v4l.org/cYH4r

4. Importing entire namespaces can't be supported: PHP has no way to know what is available in a namespace before it's been loaded.

Consider:

<?php

spl_autoload_register(function($class) {
  // ...
});

use Foo\*; // because "use Foo" would alias the \Foo class
use Bar\*; // or perhaps "import Bar"

new Baz();

?>

Which class would that try to autoload? \Baz? Foo\Baz? Bar\Baz? There's no way for PHP to know. Attempting to autoload every possible class would be a large performance hit that only gets worse with each namespace being imported. And what if Foo and Bar both defined a class with the same name? It's perfectly acceptable to do that, but trying to import both namespaces would cause inconsistent behavior at best and errors at worst.
(Which has also been said on the mailing list: http://news.php.net/php.internals/68526)

So I'll go out on a limb and say this won't happen.