The anti-Microsoft/Novell clauses are different in kind than anything that has appeared before and require a new risk assessment. Rather than merely allocate rights, those clauses are intended to encourage active participation in disrupting an existing agreement and in general promote a boycott of buying patent licenses.
Those clauses flirt with conduct that would, in other contexts, be called "tortious interference with contract," "inducing infringement" and "an agreement in restraint of trade." Most for-profit companies would not allow their employees to make such agreements as part of a trade group or industry consortium, so the unintended, as well as the intended, consequences of these clauses should be given special attention.
As noted previously in this series, there are many other open source licenses that may be more appropriate than the GPLv3 in its current form. Anyone contemplating adopting GPLv3 should seek legal advise before doing so.