I think its a bit to compact, pushed together. I think you should have divided it in more paragraphs.
But thats just my opinion.
The only really bad thing about open source operating system's security is that unless it is an extremely serious problem like easy, anyone can do it from anywhere, complete takeover of computers or networks the fixes for it will not be released till the next development cycle is over.
This isn't true, security fixes have a very high priority, and are pushed out as updates daily.
If there is for example a security hole in Firefox 4, they will not wait till Firefox 5 before its fixed. Ubuntu for example get constantly security updates (they are pushed much much faster than Windows).