Custom fields in wordpress is a surprise, with custom post type wordpress suddenly become the first choice for out-of-box CMS system.
There are many plugin around, the most of them require some medium level PHP skill to change template or theme.
Some cool plugins like Custom Post type UI, just custom post type and advanced custom type. But those plugin still have one problem to solve, how to make the input UI easier to use. One common problem is in the input screen, custom field displayed twice, and still give user flexibility to add other custom fields.
Custom field template suppose fix it, but it seems still need PHP code change somewhere.
Magic fields 2 solved this problem eventual, by introducing some style middle tables at backend, the admin UI looks much cleaner. And data storage is still in post_metadata.