As far as secure, every OS goes through vulnerability cycles during it's life time, with the lowest most secure points being right before it goes End of Life of course.
Windows 7 does show MS first real effort at starting out secure. As it remains out on the market vulnerabilities will be exposed, it be less secure than competitors for a bit, get patched be more secure, etc. etc.
The last few attempts at placing viruses on my daughter's laptop via the internet came through iTunes.