I'm not very familiar with Windows 8's security features (besides the inclusion of an improved Windows Defender and a sandbox by default).

However, what security can one speak of when it's only (enhanced) security against uninformed third parties? With features such as SmartScreen snarfing your requests, security goes only as far as the will of the vendor or their cooperation with an institution of power.

Windows malware threats still seem to be going quite consistent.

Windows XP will stop receiving security updates and 0-days will never be patched.

If my computer is letting me to play solitaire on my free time, I don't care which bot net it is contributing on its free time

Until it steals your important data, or crashes your system, or sets your laptop on fire from maxing out your cpu for bitcoin mining.

Depends on the specific malware obviously.