Cosmic complementarity: probing the acceleration of the Universe
  We assess the accuracy with which Omega and Lambda can be measured by combining various types of upcoming experiments. Useful expressions for the Fisher information matrix are derived for classical cosmological tests involving luminosity (eg, SN Ia), angular size, age and number counts. These geometric probes are found to be quite complementary both to each other and to inferences from cluster abundance and the cosmic microwave background (CMB). For instance, a joint analysis of SN Ia and CMB reduces the error bars by about an order of magnitude compared to a separate analysis of either data set. 
Max Tegmark, Daniel J. Eisenstein, Wayne Hu, Richard Kron