For the most part, you're correct although I'd like to add that Microsoft has stated that their Malicious Software Removal Tool will continue to be supported for XP through 7/14/2015 (see
http://www.microsoft.com/security/pc-security/malware-removal.aspx), so if you are still online with an XP operating system, you don't necessarily need a new OS right away... And like you said, Microsoft stopping support for XP doesn't mean that you won't be able to use it, but rather they just won't produce anymore fixes for it, and so may lead to more vulnerabilities if you plan to use it online. Also some of the newer software that they'll come out with may not be compatible with XP anymore. Right now at work, we're having to go through all of our machines and make sure that they are running at least Win 7.
I agree that Win 8 is a lot more different than older versions of Windows... That's because of their new model of "one platform for all of your devices"... They wanted something that people could use regardless of whether they were on a smart-phone, a tablet, a PC / laptop, or even their XBox One. It's more beneficial for the newer technologies that use touch screens rather than the traditional mouse and keyboard. But for those traditional PCs and laptops, many people have complained that it's more difficult to use. There is a way to switch it from the "Metro" look to the more traditional desktop, but it isn't as obvious to make the switch. I haven't had a chance to actually work with Win 8 yet, but I've got a feeling that I may soon have to learn how to use this OS...