At the end of June, Microsoft will release the first beta copies of Windows 8.1, ahead of shipping the final version before the end of the year. Win8.1 will be a free upgrade for all users of Windows 8.
If you want a sneak peek into the major new features, the mostly-excellent Ed Bott over at ZDNet has a good round-up at http://www.zdnet.com/windows-8-1-unveiled-will-it-change-your-mind-about-windows-8-7000016112/
As a user of Windows 8 since I replaced my PC recently, which I couldn't be bothered to reformat with Windows 7, I have to say that it does take some time to get used to. The most annoying feature for me is the new Start screen, which I hate, which means clicking through to the traditional desktop each time I reboot. Thankfully, the option to boot straight into the desktop, which was present in the Win8 beta builds but removed before the final release, is coming back. So I'll be first in the queue when 8.1 starts shipping.