Easiest to Learn? Ubuntu. It is catered almost toward the Windows people now that it is almost a seemless transition from Windows to Linux with that distro now.
Everyday use?
PC-BSD. while it doesnt like my hardware, it is very good.
As for the boot isuue, if you go with Ubuntu you can easily repair the BCD loader to get back the Windows loader then use EasyBCD to add ubuntu to the list. Or you can just leave GRUB on.
PC-BSD's loader is ancient and stinks....i had issues with that myself and was forced to reinstall Vista/Win7. So you might want to steer clear of that till they fix the loader.