Are Windows OS user programs vulnerable to Spectre and the other recent Intel flaws? Wouldn't the virtual memory assignment in Windows prevent such attacks, or their usefulness? Sorry if I miss something, the attacks seem complex, and not even deterministic.
Virtual addressing does not make spectre or meltdown more difficult to exploit. All of the proof of concept exploits have been performed on systems with virtual addressing. Virtual addressing by itself is not a security feature, it's merely a convenience for multitasking OS.
Page permissions are intended to provide isolation between different processes and between user-space and kernel-space, but the whole problem with Meltdown is that it provides a mechanism for leaking information across that boundary.
Rendition Infosec has built a nice slide deck describing the vulnerabilities and their implications in a condensed format.