Steven Weinberg has lately been critical of QM. He now also has a technical paper out called 'Lindblad Decoherence in Atomic Clocks', available on arxiv. Here is the abstract: It's a short paper (6 pgs of text), arguing for objective collapse (a la GRW/Diosi-Penrose/etc) instead of Copenhagen/MWI. Based on Ramsey-method atomic clocks frequency measurements, Weinberg gives upper limits (based on Ramsey transition times) for objective collapse below which the scheme is already ruled out experimentally. He also proposes two different ways in which objective collapse can be sought out further in future atomic clock experiments.