Windows Embedded CE 6.0 has been released a long, long time ago. Perusing through the OSNews archives reveals that it was released November 1, 2006 - more than three years ago. Windows Embedded CE 6.0 brought with it numerous improvements over version 5.2, partially because the kernel was completely redesigned. However, despite being over three years old, Windows Mobile is currently still using version 5.2. The Zune HD, however, does use version 6.0.
So, what, exactly, are the improvements made in version 6.0? As already mentioned, the kernel was completely redesigned, giving it support for 32768 simultaneous processes, with each process capable of supporting up to 2GB of virtual memory. Windows Embedded CE 5.2 has a maximum of 32 processes supporting a maximum of 32MB per process. CE 6.0 runs on x86, ARM, SH4, and MIPS.
Microsoft also took the opportunity to do some shifting around between kernel and userspace. Things like GWES, device driver manager, and file system manager were all moved into kernelspace to improve performance. In addition, whereas CE 6.0 supports kernelmode drivers, 5.x did not.
There are more improvements than just these, obviously, but I chose to highlight these to illustrate just how different 6.0 is from 5.2.
Another important aspect of Windows Embedded CE 6.0 is its shared source model (not to be confused with open source or Free software, by the way). The entire source code for the kernel, many of its drivers, and some higher-level parts, is available for viewing, straight from the Windows Embedded CE 6.0 distribution package.
Windows Phone 7 Series is not just a massive reboot of the Windows Mobile user experience - the core of the operating system is also a vast improvement over previous versions of Windows Mobile. As such, it simply doesn't make a whole lot of sense to call WP7S "Windows Mobile 7".
As interesting as this stuff sounds, it doesn't answer any of the burning questions regarding Microsoft's new mobile operating system, such as how (or if) it does multitasking, how application distribution is handled, and so on.