Customize the view
You
cannot edit the columns for details view in the Customize View dialog anymore, which is annoying. To pick which columns are visible you use either the View header dropdown button (where it says "Panes" at the top in a panes-type view) or right click on the column headers themselves. Both present a LONG list of columns to choose from, and you add checkmarks next to the ones you want. If you use the "right-click on the column header" method to activate a new column, it places the column in the "order" where you right clicked (which is a nice touch). And, to re-order them once they appear, you drag the column headers.
This is annoying in a view with lots of columns, where you might want to move one or more columns a great horizontal distance. Before, you could move groups of columns up and down at once by multi-selecting them in the Customize View dialog. The new mechanism is fiddly and can be very tough to manage on a trackpad or trackpoint input device.
I wish they'd bring the Details Pane manager widget back and just hide it under a "Edit details columns" button in the Customize View dialog. The drop-down and drag columns method is nicely designed and works well for a "quick fix" but if you really want to add and organize a bunch of columns, it is tiresome to deal with, and the old method was much slicker.