Thematic Theme Excerpt Read More on both manual and auto excerpt.

gistfile1.php

function childtheme_override_content() {
    global $thematic_content_length;

    if ( strtolower($thematic_content_length) == 'full' ) {
        $post = get_the_content( thematic_more_text() );
        $post = apply_filters('the_content', $post);
        $post = str_replace(']]>', ']]>', $post);
    } elseif ( strtolower($thematic_content_length) == 'excerpt') {
        $post = '';
        $post .= get_the_excerpt();
        $post .= '... <a href="'.get_permalink().'"> Read More »</a>';
        $post = apply_filters('the_excerpt',$post);
        if ( apply_filters( 'thematic_post_thumbs', TRUE) ) {
            $post_title = get_the_title();
            $size = apply_filters( 'thematic_post_thumb_size' , array(100,100) );
            $attr = apply_filters( 'thematic_post_thumb_attr', array('title'    => 'Permalink to ' . $post_title) );
            if ( has_post_thumbnail() ) {
                $post = '<a class="entry-thumb" href="' . get_permalink() . '" title="Permalink to ' . get_the_title() . '" >' . get_the_post_thumbnail(get_the_ID(), $size, $attr) . '</a>' . $post;
                }
        }
    } elseif ( strtolower($thematic_content_length) == 'none') {
    } else {
        $post = get_the_content( thematic_more_text() );
        $post = apply_filters('the_content', $post);
        $post = str_replace(']]>', ']]&gt;', $post);
    }
    echo apply_filters('thematic_post', $post);
}


function childtheme_excerpt_trailing($text) {
return str_replace('[...]', '', $text);
}
add_filter('get_the_excerpt', 'childtheme_excerpt_trailing');