Linux is my number one choice.
Who says it's not user friendly? I can tell you this, it's a hell of a lot more user friendly than DOS ever was. If you can use DOS, you can probably use Linux 10 times better.
If you're still scared of the command line, if you use a window manager such as KDE or GNOME it shouldn't be scary at all. You can still use many of your favorite programs such as Firefox. If you need to run windows apps (aka OP2) you can use WINE, a windows emulator (or even install a program like VMware, to let you run windows inside of linux).
If you worry that you are gonna screw up settings, there are plenty of 'wizard' programs that can do it all for you, both command line and graphical.
Systems like Debian, SuSE, Redhat etc all have some sort of package system for software. You need very little knowledge of linux (or even computers in general) to be able to use these.
In other words, you can have as much or as little control as you would like.
As for security, you can't really say that it's necessarily more secure than windows (right out of the box), because you can do a lot of boners that can open your whole system up for attack. However, you are still quite a bit safer considering Windows is targeted more often than Linux.
I would be using Linux right now, the only thing that keeps me from doing so is OP2 work. (I need windows for that <_< )