  Recent advances in numerical relativity provide a detailed description of the
waveforms of coalescing massive black hole binaries (MBHBs), expected to be the
strongest detectable LISA sources. We present a preliminary study of LISA's
sensitivity to MBHB parameters using a hybrid numerical/analytic waveform for
equal-mass, non-spinning holes. The Synthetic LISA software package is used to
simulate the instrument response and the Fisher information matrix method is
used to estimate errors in the parameters. Initial results indicate that
inclusion of the merger signal can significantly improve the precision of some
parameter estimates. For example, the median parameter errors for an ensemble
of systems with total redshifted mass of one million Solar masses at a redshift
of one were found to decrease by a factor of slightly more than two for signals
with merger as compared to signals truncated at the Schwarzchild ISCO.
