  We combine recent long Gamma Ray Bursts (GRBs) sample including 52 objects
out to z$=$6.3 compiled from Swift Gamma Ray Bursts by Schaefer (2006) with
Type Ia Supernova (SNIa), Cosmic Microwave Background (CMB) and Baryon
Oscillation (BAO) to constrain cosmologies. We study the constraints arising
from GRBs alone and the complementarity of GRBs to other cosmological probes.
To analyze the cosmological role of GRBs, we adopt the Hubble constant as a
free parameter with a prior in the range of $H_0=72\pm8\enspace\kmsmpc$ instead
of a fixed $H_0$ used in previous studies. By jointly using SNIa gold/SNLS
samples and GRBs, the constraints on \Om -\Ol parameter space are dramatically
improved in comparing with those from SNIa data alone. The complementarity of
GRBs is mostly from the sub-sample with z$>$1.5 due to the different parameter
degeneracies involved in luminosity distances at different redshifts. Including
GRB data in addition to SNIa, BAO and CMB in our analysis, we find that the
concordance model with \Om $\sim$0.3 and \Ol$\sim$0.7 is still well within
1$\sigma$ confidence range.
