The program we call Photoshop (be it Elements, CS-Standard or CS-Pro) is a monstrous collection of code, built to run on both Windows (XP, Vista, 7 and now 8, with 32 and 64 bit flavors) and OS X (predominantly 64 bit) with some parts dating back to the days of 16 bit processors. Times change and computers advance, and Adobe has been updating their codebase and migrating to 64 bit compliant tools. Adobe has also been striving to make the user interfaces more consistent across platform and versions. I recall several "ancient" versions of programs that modified the Photoshop interface. Since Adobe created the "CS"-series, interface hacks have been frowned upon.
I am grateful for the real advances and more advanced techniques that provide more than just glitz and feature creep. One of the biggest casualties of the migration comes from the tool used to create the pallets. The new pallets require more screen real estate compared to the 32bit pallets. The new codebase has invalidated some of the third party user interface additions.
Additionally, Apple's move to Retina displays has forced Adobe to start creating yet another set of all UI elements at double resolution, taking time away from other less-pressing programming projects.