Was Einstein 100% right ?
  The confrontation between General Relativity and experimental results, notably binary pulsar data, is summarized and its significance discussed. The agreement between experiment and theory is numerically very impressive. However, some recent theoretical findings (existence of non-perturbative strong-field effects, natural cosmological attraction toward zero scalar couplings) suggest that the present agreement between Einstein's theory and experiment might be a red herring and provide new motivations for improving the experimental tests of gravity. 
T. Damour