meta_query, number comparison, not quite working as it should

Question

I have a wp_query that gets all custom post types in ascending order from today, to list some events on a site of mine. While this works fine:

 $args = array( 'post_type'         =>  'events',
                                'posts_per_page'    =>  5,
                                'orderby'           =>  'meta_value', 
                                'order'             =>  'ASC',
                                'meta_key'          =>  'my_special_date',
                                'meta_value'        =>  date('Ymd',strtotime("today")),
                                'meta_compare'      =>  '>=' ); 

I am not getting the same results when I convert this to using meta_query, like so:

array(  'post_type'         =>  'events',
                'posts_per_page'    =>  5,
                'orderby'           =>  'meta_value', 
                'order'             =>  'ASC',
                'meta_query'        =>  array(
                                                array(
                                                        'key'           => 'my_special_date',
                                                        'value'         => date('Ymd',strtotime("today")),
                                                        'compare'       => '>=',
                                                        'type'          => 'NUMERIC'
                                                        )

                                            )

                 ); 

Note that I'm not comparing dates, I'm comparing numbers, as the date is in the Ymd format. the meta key is in this format. I am having some rather odd results from this - I can't quite work out what's wrong. Anything look obviously wrong to any of you?