Water Heater Advice Needed

The plumber recently pronounced my domestic hot water heater dead, and I'm looking for the best replacement solution. Since I just replaced my radiant boiler a few years ago with a new Teledyne-Laars boiler I'm not interested in a "combo" solution, just one for the domestic hot water.

Are the "tankless" models that I've seen many people discuss appropriate for domestic hot water only, or are they only useful in a combined radiant heat/domestic hot water situation?

Does anyone have (please email) a recommendation for a plumber in the Sunnyvale area who could do either a conventional water heater installation or is experienced with the newer alternative solutions?

Thanks,
Andrew