  We argue that while fluctuating fronts propagating into an unstable state
should be in the standard KPZ universality class when they are {\em pushed},
they should not when they are {\em pulled}: The universal $1/t$ velocity
relaxation of deterministic pulled fronts makes it unlikely that the KPZ
equation is the appropriate effective long-wavelength low-frequency theory in
this regime. Simulations in 2$D$ confirm the proposed scenario, and yield
exponents $\beta \approx 0.29\pm 0.01$, $\zeta \approx 0.40\pm 0.02$ for
fluctuating pulled fronts, instead of the KPZ values $\beta=1/3$, $\zeta =
1/2$. Our value of $\beta$ is consistent with an earlier result of Riordan {\em
et al.}
