Sure, I'll give you more quantified findings.
Major Changes:
-Now boots to 64 bit Kernel regardless of EFI type
-Updated graphics drivers
-Further implementation of Core Animation, leading to efficient scrolling and animations system-wide
-OpenGL updated
-Memory manager updated
Core changes generally aren't well documented for the end user.
Why not expect major overhauls? Previous releases have incorporated what I'd call "essential service APIs" to modernize OS X along the years. These APIs also made hardware more accessible to developers with less layers needed in an application's codebase. However, it seems Apple has its bases covered here. All processing hardware is now accessible through Core Image, Audio, Animation, essential user services have an API through Core Data, and apps are being written to these APIs every day through the Mac App Store. Considering that Apple has the bases covered, what more must be done?
Networking software is up-to-date in the system and Apple uses their own proprietary API for things like iCloud syncing. Seeing as the focus of Apple's future is less on the computer sitting on your desk and more about the things it does, I don't expect them to do much other than take away conventional computing workflow and mechanisms. Furthermore, the base of the OS, NeXTSTEP, is about two decades old now. The Kernel is still getting updated but again is nothing new. These are the kinds of things that prevent a total overhaul of an OS and cannot be changed without, again, a total overhaul. I'm talking about an overhaul down to the file system used (ZFS anyone?), how systems files are encoded, distribution models, core media decoding services, coding languages, catering to next-gen hardware, etc. Think OS 9 to OS X. Hence, why I say don't expect any major overhauls until OS XI, if it ever exists.
I hope this clarified my post for you.
Not really