Yes, windows 8 does have some nice improvements under the hood. That said, when you have to buy separate programs to provide the basic functionality you need.... there's a problem. You just turned Windows 8 back into Windows 7 for the most part. Metro is not user friendly. Seriously, just ask someone to find the "shutdown" command. BTW, if anyone needs a free, open source start menu replacement for Windows 8, - http://www.classicshell.net/
I don't like the direction Microsoft is going, which is a walled garden of apps directly linked to your name, address and credit card #. It's a major violation of privacy in my book. I think eventually the idea is to lock out any unauthorized app that's not from their store. If I wanted an ipad... I'd buy one.
The metro start menu is actually customizable enough to be useful on a PC, if a bit jarring when you're jerked from the desktop back to Metro, it's just the apps that are worthless (on a PC). If Microsoft had included the normal start menu as an option, (even as a registry switch) I think it could have avoided a lot of criticisms.
As for security, I haven't found it any more or less secure than Windows 7. I do know I haven't had to fix as many Windows 8 problems because... well... no one uses it and those that do usually request a "downgrade" request to Windows 7.