A bookmarklet that will let you choose to hide or not the @replies on a Twitter timeline.

strip_replies_advanced.js

// You will find the draggable version there: http://bookmarklets.heroku.com/bookmarklets/1798

(
    function( $ )
    {
        var removedTweets  = [],
            $button        = null,
            interval       = null;
        
        insertButton();
        hideReplies();
        
        function hideReplies()
        {
            if( !interval )
            {
                interval = window.setInterval( hideReplies, 250 );
            }
            
            // This could surely be improved by fetching only tweets containing an element with '.reply-icon'.
            $( '.tweet-text:visible' ).each(
                function()
                {
                    var $this = $( this );
                    
                    if( $.trim( $this.html() )[ 0 ] === '@' )
                    {
                        removedTweets.push(
                            $this.closest( '.stream-item' ).fadeOut( 'fast' )
                        );
                    }
                }
            );
        }
        
        function putRepliesBack()
        {
            window.clearInterval( interval );
            interval = null;
            
            for( var i = 0; i < removedTweets.length; i++ )
            {
                removedTweets[ i ].fadeIn( 'fast' );
            }
            
            removedTweets = [];
        }
        
        function insertButton()
        {
            $button = $( '<a id="rr-button" class="rr-put-back" href="#">Put @replies back</a>' );
            
            $button.css(
                {
                    position      : 'fixed',
                    bottom        : 0,
                    right         : 0,
                    display       : 'inline-block',
                    background    : '#444',
                    color         : '#FFF',
                    padding       : '0px 5px',
                    textTransform : 'uppercase',
                    zIndex        : 7800
                }
            );
            
            $button.hover(
                function()
                {
                    $( this ).css( 'textDecoration', 'underline' );
                },
                function()
                {
                    $( this ).css( 'textDecoration', 'none' );
                }
            );
            
            $button.click( function()
            {
                if( $button.hasClass( 'rr-put-back' ) )
                {
                    $button.html( 'Hide @replies' );
                    $button.removeClass( 'rr-put-back' ).addClass( 'rr-hide' );
                    
                    putRepliesBack();
                }
                else
                {
                    $button.html( 'Put @replies back' );
                    $button.removeClass( 'rr-hide' ).addClass( 'rr-put-back' );
                    
                    hideReplies();
                }
            } );
            
            $( 'body' ).append( $button );
        }
        
    }
)( jQuery );

Here is the draggable version: http://bookmarklets.heroku.com/bookmarklets/1798