Tankless water heater?

Need to replace my old water heater (I'm not talking about the radiant system here), and I want to go green.

The newer tankless systems look promising, but do they work well with Eichlers (considering that the water pipes are routed in the slab)?

Gas or electric? Any recommendations for brand?

Is it adviceable to install additional local water heaters, for instance in the bathroom (to immediately get hot water in the shower).

Thanks,
Gloria