This type of UIs are frequently displayed in various web-Sites and .net books.
Are these types of User-Interfaces acceptable and/or popular in commercial and/or customized Business Software?
Please note
(1) the use of Binding Navigator, and
(2) the placement of Master-grid, Detail-grid and Input Area in the same form.
To me a search facility is always needed no matter how trivial the UI is, which is not available here. And of course I don't find any relevance of using a Binding Navigator in any UI that deals with huge data.
Missing search was the first thing I noticed too.
So I think you need an advanced search for the main grid, as well as filter and sort options for columns.
With regards to the master-detail, it may be more intuitive to have the ability to select (double click/enter) from the main grid and that would bring up the details for the order to edit, as well as a similar grid with order details.
The reason that is more intuitive is because the user is dealing with a separate window each time - allowing them to deal with the task in hand, without being bashed over the head with a cluttered main window with everything crammed in.