If you want to go for an Ubuntu based GNU/Linux distribution, I'd recommend
Kubuntu, as KDE is older (believe it or not) and more refined (in my opinion) than Desktop Environments such as GNOME.
For me, going from Kubuntu to Windows is a much steeper learning curve than vice versa.
If you've heard that Ubuntu isn't user friendly, then you should really know that this hasn't been much of a problem since MS DOS was facing similar issues. The Ubuntu Software Centre (or Muon in Kubuntu, though I feel it inferior to KDE's own Apper) has pretty much any software that you may need to install. Even if it doesn't, then you can simply go searching for a .deb installer, which is similar to .msi in Windows.
Kernel mode is often described as one of the nightmares of GNU/Linux, but it really is only needed in cases where you'd have to reboot in Windows.
There is also a graphical browser available in Kernel Mode which uses framebuffer, called
NetSurf. Unfortunately, it has a monstrous list of dependencies which all have their own monstrous list of dependencies, which have to be installed using the terminal. It isn't all that hard, just incredibly tedious.
For now, gaming is limited primarily to Windows, but Valve are in the middle of creating a client that will work on GNU/Linux, so Steam's huge gaming library may soon be available even on Ubuntu.
In short, I'd recommend Ubuntu for a standard user, as the advantage of Windows lies in its rich source of applications, many of which will be completely useless for a standard user. If you need the applications that only Windows can use, then use Windows. Even if you do need Windows, you can dual boot the two Operating Systems by partitioning your hard drive and installing *Ubuntu on one and Windows on the other.