There are probably 3 main areas of differences between the various Linuxes I've used. The big one is the "window manager" - it may be Ubuntu's unity (not a fan); Gnome (not a fan); Gnome classic (not bad IMHO); and KDE (wildly configurable but quite usable out of the box). I haven't used the xface etc. interfaces. For basics, Gnome classic and KDE are very usable, not exactly like windows but pretty close. The average user will pick up the differences quickly.
The next area of differences is in the supporting applications/configuration. Each distro seems to have its own take on where to put various configuration options. Generally it is somewhere under the main menus, in some kind of system/settings/etc. A little annoying to find where your distro puts them, but once found no problem.
Finally, the other difference is in the updates/packaging. Generally these fall into .deb or .rpm camps. For some users you may never know or care. Some will eventually end up at a command line, cutting/pasting arcane commands from a website trying to configure something or other.
I don't miss windows at home. I've been running one flavor or another of Linux as my primary home desktop OS for 6 or 8 years now. I'm writing this on an old Dell Dimension e510 running Mint 16.
What would you say could serve as a decent ‘winxp’ empulator?