Summary from several evaluations below:

http://www.networkworld.com/news/2013/053013-microsoft-outs-the-new-features-270303.html

http://www.eweek.com/enterprise-apps/start-button-returns-in-windows-8.1/

http://www.informationweek.com/windows/operating-systems/windows-81-restores-start-button-with-tw/240155767?cid=nl_IW_daily_2013-05-30_html

http://www.pcmag.com/article2/0,2817,2419698,00.asp

http://www.zdnet.com/windows-blue-whats-new-on-the-search-front-7000016075/

http://www.zdnet.com/windows-8-1-unveiled-will-it-change-your-mind-about-windows-8-7000016112/

QUOTE: Microsoft announced Thursday that Windows 8.1 will restore the Start button and include a boot-to-desktop option, confirming a series of reports published the previous afternoon.  At face value, the tweaks smooth over several of Windows 8’s most-criticized rough edges. What remains to be seen, however, is if the new features’ implementations will mollify detractors, or merely shift criticism for the OS, which has struggled to gain users, in a different direction.

START BUTTON: Desktop diehards will find a present waiting for them in Windows 8.1, the impending upgrade colloquially dubbed “Windows Blue.” A wonderful, horrible, oh-so-teasing present. The Start button is back–but the Start menu isn’t. Instead, clicking the old familar button will dump you into the modern UI Start screen. While the new feature is notable for adding a helpful visual cue to an operating system rife with hidden menus, it isn’t exactly what people begging for the return of the Start button were looking for

BOOT DESKTOP MODE: The modern-style PC setting options is also getting a big boost. One of the biggest complaints about Windows 8 is the way it constantly swaps you back and forth between the desktop and modern interfaces, a problem exacerbated by the fact that you have to dive into the desktop control panel to tinker with under-the-hood stuff. No more.

IE11: Internet Explorer 11 will make its debut in Windows 8.1, as well. While most of the tweaks sounds fairly basic–faster page loads, better touch performance–it’s also adding the tab syncing feature seen in leaked builds of Blue, allowing you to open tabs across multiple Windows 8.1 PCs and tablets.

DEVICE SYNC: Speaking of, Windows 8.1 also adds the ability to sync your settings and Start screen apps across multiple devices, assuming you sign in to those devices using an online-connected Microsoft account.

TILE RE-SIZING: More minute improvements include more Live Tile sizing options, additional category filters in the All Apps screen, and a plethora of Start screen tile shuffling options.

SLIDE SHOW – sneak preview of new features http://www.networkworld.com/slideshow/100153/windows-blue-a-sneak-peek.html