Maybe "commonly encountered Free Software desktop and server userspace components"? After all, much of that is what you will also find on BSDs et al., and will give you the same trouble (if any) there.

The Linux kernel itself is in fact very, VERY extensively backwards-compatible, which is why I find it particularly unfair (on top of being wrong) to use the label Dalewyn did. It's the installed userspace libraries that aren't - at least not in all cases, but the situation sure has improved a lot over the last decade or so.

Ubuntu, Gnome, etc