Below is the syntax for a simple skin for version 6.x-2.x:

; Menu styles
skinr[MYTHEME_menus][title] = Menu styles
skinr[MYTHEME_menus][type] = select
skinr[MYTHEME_menus][group] = links
skinr[MYTHEME_menus][features][] = block
skinr[MYTHEME_menus][features][] = panels_pane
skinr[MYTHEME_menus][features][] = views_view
skinr[MYTHEME_menus][description] = select from available menu styles
skinr[MYTHEME_menus][options][1][label] = One level links with separators
skinr[MYTHEME_menus][options][1][class] = inline-links
skinr[MYTHEME_menus][options][2][label] = Links as columns with sub-options below
skinr[MYTHEME_menus][options][2][class] = column-links clearfix

This is how to implement that skin for 7.x-2.x:

 * Implements hook_skinr_skin_info().
function MYTHEME_skinr_skin_info() {
$skins['MYTHEME_menus'] = array(
'title' => t('Menu styles'),
'description' => t('Select from available menu styles.'),
'type' => 'select',
'group' => 'MYTHEME_links',
'default status' => '1',
'theme hooks' => array('block', 'panels_pane', 'views_view', 'region'),
'options' => array(
'inline-links' => array(
'title' => t('One level links with separators'),
'class' => array('inline-links'),
'column-links' => array(
'title' => t('Links as columns with sub-options below'),
'class' => array('column-links', 'clearfix'),

You'll notice here theres basic info about the skin, a group listed and options. Something not present in the 6.x-2.x syntax is default_status which basically tells Skinr whether or not this should appear in the UI by default. This option is not required, by default all skins are disabled and can be enabled via the UI. Additionally features are now called theme_hooks, which is a more sensible description for what this option does. For a complete rundown of options for skins and whats required and not required click here.