Well "slams" isn't exactly accurate however he is right in saying Windows 8 is still a pretty big work in progress for Microsoft however they had to release this year. It is a stable OS however it is a little schizophrenic to use with the awkward way that Metro (Modern UI) has been crowbarred into it.

In my opinion Windows 8 is more of a technology/strategy preview and not a "real" Windows release. I have been running the RTM since it hit MSDN and it is fine to use as a primary OS however it isn't all that nice to use as your primary OS. There are so many rough edges and inconsistency’s it is quite frustrating to use at times. However this is Microsoft trying to work out how Windows will work on tablet/touch based devices so it is to be expected.

Other than developers wanting to get used to some of the new development options available with WinRT and people who want Windows on a tablet and not iOS or Android I don't see any real reasons to upgrade from Windows 7. Especially as Windows 7 is a nicer experience for desktop/laptop users IMHO.